BIOL Final Flashcards
(504 cards)
1
Q
Populations _______. Individuals ______.
A
Evolve, adapt
2
Q
What is the smallest unit that can evolve?
A
A population.
3
Q
Evolution can be measured only as the accumulation of changes in ___________.
A
in a population
4
Q
What are Darwin’s Postulates that natural selection was based on?
A
- variation in phenotype exists among individuals
- High reproductive potential means populations increase geometrically
- Individuals compete for limited resources
- “Fit” offspring with characteristics matching current environment more likely to survive and reproduce
5
Q
What are the assumptions of evolution?
A
- natural selection acts on phenotypes in a generation therefore variation is heritable for natural selection to lead to evolutionary change
- small evolutionary changes in populations occur quickly but complex ones take thousands of generations
- Earth’s long age makes this possible
6
Q
What are the different categories of what is utilized for evidence of evolution?
A
- Fossil records
- Comparative anatomy
- Biogeography
- Comparative embryology
7
Q
What are fossil records utilized for evolution and what is their setback?
A
evolution observed from common ancestors to current living organisms
fossilization is rare especially in soft species makes this challenging
8
Q
what is comparative anatomy and what is utilized for?
A
reveals existence of homologous structures “shared ancestry” beneath phenotypically different characters indicating shared origin
9
Q
Relevance of humans influencing evolution through artificial selection
A
men create new species from an ancestor by selecting the best variants in the population for further breeding
ie “Brassica” selected for large compact flowering stalks broccoli cabbage etc
10
Q
Explain the soapberry bug example
A
bug feeding apparatus changed when the bugs transitioned from balloon vine fruit to flat podded golden rain fruit
when bugs were taken to the lab, change persisted
change was an adaption not phenotypic plasticity
the flat podded golden rain fruit lead to smaller beaks so the smaller beaks were favored in those birds
offspring retained parental beak lengths confirming genetic evolution change in allele frequency over time
11
Q
The oldest fossils are found
A
in the deepest strata
12
Q
What are the characteristics of Bacteria?
A
single celled
monophyletic (share a common ancestor)
has cell wall
no nucleus
no mitochondria
no chloroplasts
13
Q
What are the characteristics of Archaea?
A
single celled
monophyletic (share a common ancestor)
has cell wall
no nucleus
no mitochondria
no chloroplasts
14
Q
What are the characteristics of Protists?
A
Single celled
are polyphyletic meaning they come from different ancestors
some have cell walls cell membranes some don’t
has nucleus
has mitochondria
some have chloroplasts
15
Q
Describe the setbacks of being a single cell
A
limited ability to alter anatomy, limited capacity to extend nicheches, genetic acquisition is random
16
Q
what is some evidence of endosymbiosis?
A
DNA sequencing analysis shows a relationship between mitochondria and non-sulfur purple bacteria; chloroplasts and cyanobacteria
17
Q
How did mitochondria affect endosymbiosis?
A
- mitochondria are selfish
- produce toxic ROS
- toxicity leads to nucleus creation and evolutionary trade offs
- drove for selection for:
migration of mtDNA to nucleus, maintenance of a nuclear envelope, formation of peroxisomes, evolution of more DNA repair mechanisms
18
Q
What is evolution?
A
The accumulation over time of inherited changes in a population leading to species which are related.
19
Q
Why is evolution considered a unifying theme of biology?
A
It provides the tools to understand why everything in biology is shaped the way it is.
20
Q
What is Darwinian fitness?
A
An individual’s ability to survive to reproduction.
21
Q
What is a population?
A
A group of organisms of a single species living in the same geographical area.
22
Q
What is a species?
A
A group of organisms with common ancestry and physical structures that are able to breed and have fertile offspring.
23
Q
What is a community?
A
A group of populations composed of organisms with common ancestry sharing similar structures, functions, and behaviors.
24
Q
What is an ecosystem?
A
An interactive system composed of one or more communities and their abiotic environment.
25
What is the biosphere?
All of Earth’s ecosystems considered together.
26
What are the three goals of evolutionary biology?
1. Explain the unity of life 2. Explain the diversity of life 3. Explain how species became well adapted (adaptation).
27
What is adaptation in evolutionary biology?
The explanation of how species became well adapted to their environments.
28
What is essentialism?
The idea that organisms are created in species form and life is designed as is.
29
What did Linnaeus find?
Ancestral forms reflect evolutionary relationships.
30
Who was Darwin and what did he contribute to biology?
He developed conclusions of the origin of species and postulates on how evolution occurs.
31
Why is there a struggle for life, according to Darwin?
Because resources are limited in real life.
32
What causes variation in a population?
Individuals of any species show variation, part of which is heritable.
33
What is differential reproductive success?
The idea that better-adapted individuals are more likely to produce offspring.
34
What determines fitness according to Darwin?
The ability to reproduce and pass on traits, not just survival.
35
What is the role of heritability in evolution?
Heritable traits must exist for selection to act upon
36
Who was Thomas Malthus and how did he influence Darwin?
He observed that populations grow faster than food supply, leading to a struggle for existence.
37
What is the smallest unit that can evolve?
A population.
38
Who evolves: individuals or populations?
Individuals adapt populations evolve
39
What does natural selection act on?
Phenotypes within a generation.
40
Why is Earth's long age important to evolution?
It allows time for complex evolutionary changes to accumulate.
41
What dictates who is more fit in a population?
The environment.
42
What are Darwin's postulates?
1. Phenotypic variation exists 2. Populations increase geometrically 3. Individuals compete for resources 4. Fit individuals reproduce more.
43
What are the main types of evidence for evolution?
Fossil records, comparative anatomy, biogeography, and comparative embryology.
44
What do fossil records show?
Evolution from common ancestors to current living organisms.
45
Why is fossilization rare?
Especially in species with soft bodies.
46
What does comparative anatomy reveal?
Homologous structures that indicate shared ancestry.
47
What is homology?
Shared ancestry beneath phenotypically different structures.
48
Does similar function always mean homology?
No, similar function does not mean shared ancestry.
49
What is biogeography?
The study of the distribution of organisms
50
What did Darwin's biogeography observations suggest?
Organisms evolved from common ancestors restricted to specific areas.
51
What is comparative embryology?
The study of how organisms with a common ancestor have different adult structures but share common embryonic stages.
52
What does "ontology recapitulates phylogeny" mean?
Developmental stages reflect evolutionary history; organisms show traits from ancestors during development.
53
What example supports comparative embryology in humans?
Human embryos have gill ridges and long tails, suggesting aquatic ancestry.
54
What is EVO DEVO?
The evolution of development; it studies how development reveals evolutionary relationships
55
What is molecular biology?
The study of life’s molecular building blocks like DNA, RNA, proteins, and how they show shared ancestry.
56
What is LUCA?
The Last Universal Common Ancestor of all current life forms.
57
What is phylogenetics?
The science of classifying organisms based on shared traits to show evolutionary relationships.
58
Do species evolve from one another in phylogenetics?
No, species share a common ancestor, like cousins sharing grandparents.
59
What is convergent evolution?
When unrelated species independently evolve similar traits due to similar environmental pressures.
60
What are analogous traits?
Traits that serve similar functions but do not come from a common ancestor.
61
How do humans influence evolution through artificial selection?
By breeding organisms with desirable traits, leading to new species.
62
What is an example of artificial selection in plants?
Brassica plants were selectively bred into broccoli, cabbage, etc.
63
What happened in the Soapberry Bug example?
Their beaks evolved to be shorter due to a change in food source, showing genetic evolution.
64
Was the Soapberry bug change due to phenotypic plasticity?
No, the change was genetic and heritable, not plastic.
65
What is phenotypic plasticity?
Non-heritable changes in traits, like skin color changing due to sun exposure.
66
How old is Earth?
Approximately 4.6 billion years old.
67
What was needed for life to evolve?
The presence of macromolecules like nucleic acids and proteins.
68
Where did the first organic molecules come from?
Simulated early Earth conditions: no oxygen, lots of methane, ammonia, water, and lightning.
69
What is the proposed sequence of early life formation?
Inorganic molecules → organic molecules → self-replicating RNA → lipid aggregations → progenote → LUCA.
70
What are prokaryotes?
Single-celled organisms with limited anatomical variation and random genetic variation acquisition.
71
What are eukaryotes?
Organisms with internal membrane-bound organelles, arising from protists through serial endosymbiosis.
72
What is the endosymbiosis hypothesis?
The idea that mitochondria and chloroplasts originated from bacteria living inside another cell in a mutually beneficial relationship.
73
What evidence supports endosymbiosis?
DNA similarities between mitochondria and purple bacteria, and chloroplasts with cyanobacteria.
74
Why are mitochondria considered selfish?
They have efficient metabolism but produce toxic ROS, leading to evolutionary changes in the host cell.
75
What changes occurred due to mitochondrial toxicity?
Evolution of nuclear envelope, mtDNA migration, peroxisomes, and DNA repair mechanisms.
76
How are mitochondria inherited?
Through the egg; the egg evolved to be large enough to pass them on.
77
Why was sexual reproduction selected for?
To ensure another partner invested in gametes, aiding mitochondrial transmission.
78
What is macroevolution?
Long-term evolutionary divergence leading to the formation of new taxa.
79
What are the two forms of macroevolution?
Gradualism and punctuated equilibrium.
80
What is gradualism?
Evolution through slow, continuous changes over a long period.
81
What does the fossil record suggest about evolution?
Evolution occurs in bursts (punctuated equilibrium), not gradually.
82
What is punctuated equilibrium?
Long periods of stability interrupted by short bursts of rapid species turnover.
83
What causes adaptive radiations?
The appearance of new adaptive zones and opportunities after mass extinctions.
84
What causes mass extinctions?
Catastrophic biotic and abiotic events that drastically reduce species diversity.
85
What mechanisms promote punctuated equilibrium on a smaller scale?
Rapid genetic change and drift, significant genetic changes like aneuploidy or developmental mutations, and small population + new environment = adaptive evolution.
86
What was a major milestone in the history of life?
Evolution of multicellularity.
87
What allowed for the evolution of eukaryotes from archaea?
Formation of nuclear envelope from membrane invaginations and endosymbiotic organelles for metabolic efficiency.
88
What are the advantages of multicellularity?
Specialization, increased size, resource harnessing, communication, attachment, and gene regulation.
89
What types of tissues result from multicellular specialization?
Epithelial, connective, muscle, and nervous tissues
90
What was the Cambrian explosion?
A period where Earth saw a rapid diversification of life and appearance of modern body plans.
91
What organisms appeared during the Cambrian explosion?
Arthropods, segmented body plan species with head, thorax, etc.
92
From what did plants likely evolve?
Protists related to modern green algae.
93
What are key features of plants?
Vascularization for nutrient transport and seeds for reproduction (gymnosperms vs. angiosperms).
94
What is the order of colonization of land?
Aquatic protist → land plants → arthropods → land vertebrates.
95
Why was colonizing land difficult for early organisms?
They had to maintain structure without the buoyancy of water.
96
What is an extinction?
The loss of species en masse or as individual loss of diversity.
97
How many mass extinctions have occurred?
Five.
98
What is a mass extinction?
When the extinction rate exceeds the rate of speciation.
99
What was the most extensive extinction event?
The Permian-Triassic extinction (90% of species killed off).
100
What can cause extinction events?
A cascade of abiotic or biotic factors decreasing species diversity.
101
What is a potential benefit of extinction?
Opens up niches and allows adaptive radiation driving speciation.
102
How long does recovery after extinction take?
4–6 million years to begin up to 30 million to complete.
103
What is adaptive radiation?
A period of evolutionary change when organisms form new species to fill different ecological roles.
104
How did the evolution of land plants affect arthropods?
It triggered adaptive radiation in arthropods.
105
How are complex traits selected for or against?
Selection works against the worst traits not necessarily for perfection.
106
What is the role of ancestral traits in selection?
Organisms inherit a "toolbox" and must work with or improve what they have.
107
What must variation be for natural selection to work?
At least partially heritable.
108
Why do complex adaptations take time?
They require the accumulation of multiple genetic changes over many generations.
109
Is natural selection the only evolutionary mechanism?
No. Other mechanisms include sexual selection, genetic drift, random mutation, and gene flow.
110
How does sexual selection influence evolution?
It is a strong selective force often favoring traits that increase mating success.
111
How does drift affect evolution?
It's random and especially impactful in small populations with low variation.
112
What is the ultimate source of variation?
Random mutations.
113
How does gene flow affect populations?
It reduces genetic drift and mixes alleles between populations.
114
How is genetic variation introduced?
Through mutations, gene flow, and sexual reproduction.
115
What determines variation levels in populations?
The percentage of multiallelic loci and heterozygosity.
116
What does macroevolution act on?
Variation between populations especially geographical differences.
117
Where do genetic variations originate?
Mutations—changes in DNA sequences.
118
How can new alleles become dominant?
If they are naturally selected for they can take over the gene pool.
119
What is the antibiotic resistance case study an example of?
Evolution in real time.
120
Why do bacteria evolve resistance quickly?
High reproduction rate high genetic exchange
121
How is antibiotic resistance acquired?
Through prior exposure and mutations altering antibiotic targets.
122
Does variation precede selection in antibiotic resistance?
Yes selection only acts on traits that already exist.
123
What happens to resistance when antibiotic use is reduced?
Resistance is lost.
124
Why is sexual reproduction important for variation?
It is a major source due to random mating and recombination.
125
What processes introduce variation during sexual reproduction?
Random segregation of chromosomes and meiotic recombination.
126
When is sex disadvantageous?
When genes are already optimal—it may disrupt good combinations.
127
When is sex advantageous?
When the environment is unpredictable or genes are suboptimal—it creates genetic diversity.
128
What is asexual reproduction?
Reproduction with one parent, no genetic variation, occurs in lower organisms, and is quicker.
129
What is sexual reproduction?
Reproduction with two parents, produces genetic variation, occurs in more complex organisms, and takes longer.
130
What do sexual and asexual reproduction have in common?
Both produce offspring, the offspring grow and develop, and both use DNA to create new life.
131
Which type of influenza is the most mutable and problematic?
Influenza A.
132
What is genetic drift?
Changes in allele frequencies in a population that are not due to selection.
133
What is antigenic drift?
Small mutations that accumulate in a virus over time, leading to seasonal flus.
134
How is antigenic drift detected?
By classifying viral variants using loci (genes).
135
What is antigenic shift?
Sudden major genomic changes due to reassortment of viral genes, leading to novel flu strains.
136
What causes antigenic shift?
Reassortment of viral genomes during co-infection with different strains.
137
What is balanced polymorphism?
The active maintenance of multiple alleles in a population due to heterozygote advantage or varying environmental pressures.
138
Why is genetic variation important for survival?
It helps populations adapt to environmental changes and reduces risk of extinction.
139
What are the sources of genetic variation?
Mutations, chromosomal rearrangements, and sexual reproduction.
140
How does diploidy maintain variation?
It protects recessive, incompletely dominant, or codominant alleles in heterozygotes, maintaining multiple alleles.
141
What is the advantage of having two alleles (diploidy)?
It allows heterozygotes to have higher fitness than either homozygote, maintaining diversity in the population.
142
Why is genetic diversity crucial in changing environments?
It gives the population a better chance of survival by providing a wider range of traits.
143
What are patchy environments?
Environments with spatial variation in factors like background coloration, predators, or resources.
144
How do patchy environments promote balanced polymorphism?
Different genotypes are favored in different areas, maintaining multiple alleles in the population.
145
What is spatial heterogeneity?
The presence of varying conditions in different areas that apply different selective pressures.
146
What is differential selection in patchy environments?
Different environmental patches favor different genotypes, preserving genetic diversity.
147
What is gene flow?
The movement of individuals (and their alleles) between populations introducing alleles to new areas.
148
How can migration affect allele frequency in populations?
A: Migration can introduce alleles favored in one area to areas where they might be less advantageous influencing local selection.
149
What is balancing selection?
A: A form of natural selection where multiple alleles are maintained in the population because no single genotype is consistently favored.
150
How does balancing selection relate to mixed moth populations in forests?
A: Forests with light and dark trees are better colonized by mixed dark and light moths showing the advantage of genetic diversity.
151
Q: What does balancing selection maintain in populations?
A: Polymorphism (multiple alleles).
152
Q: What is frequency-dependent selection?
A: A type of selection where the fitness of a phenotype depends on its frequency in the population.
153
Q: How does frequency-dependent selection help maintain genetic variation?
A: Rare variants have a fitness advantage and increase in frequency preventing dominance of any single allele.
154
Q: Why is variation good under frequency-dependent selection?
A: Rare traits can be advantageous and allow for better adaptation (e.g. prey escaping or predators hunting better).
155
Q: What is heterozygote advantage?
A: When the heterozygous genotype (e.g. Aa) has higher fitness than either homozygous genotype (AA or aa).
156
Q: How does heterozygote advantage maintain harmful alleles in a population?
A: Because heterozygotes are fitter the harmful allele remains in the gene pool even if homozygotes suffer.
157
Q: Why is sickle cell anemia a classic example of heterozygote advantage?
A: Heterozygotes (HbAS) are resistant to malaria giving them a survival advantage in malaria-endemic areas.
158
Q: What happens to individuals with two sickle cell alleles (HbSS)?
They suffer severe symptoms, chronic pain and organ damage
159
Q: What does Hardy-Weinberg equilibrium describe?
A: A population not evolving; allele and genotype frequencies remain constant unless affected by outside forces.
160
What are the Hardy-Weinberg equations?
Allele frequency: p + q = 1
Genotype frequency: p² + 2pq + q² = 1
161
What do p², 2pq, and q² represent?
p² = Homozygous dominant genotype frequency
2pq = Heterozygous genotype frequency
q² = Homozygous recessive genotype frequency
162
What indicates that a population is evolving?
Deviation from Hardy-Weinberg equilibrium.
163
What is microevolution?
A generation-to-generation change in allele frequency in a population.
164
Does evolution always mean improvement?
No, evolution includes changes that may lead to extinction or no immediate phenotypic change.
165
What are forces that disrupt Hardy-Weinberg equilibrium?
Non-random mating, genetic drift, migration, mutation, and natural selection.
166
What is non-random mating?
Mating influenced by genotype or phenotype, not by chance.
167
What are two types of non-random mating?
Inbreeding and assortative mating.
168
How does inbreeding affect a population?
Reduces heterozygotes and increases risk of rare recessive defects but doesn't change allele frequency.
169
What is inbreeding depression?
Reduced fitness due to increased homozygosity for harmful alleles.
170
What is assortative mating?
Mating between individuals with similar traits, reducing heterozygosity.
171
Q: What is genetic drift?
A: Random changes in allele frequency due to sampling error, especially in small populations.
172
Q: How is drift different from selection?
A: Drift is random; selection is based on fitness.
173
Q: What are two types of genetic drift?
A: Bottleneck effect and founder effect.
174
Q: What is a bottleneck effect?
A: A sharp reduction in population size that reduces genetic diversity.
175
Q: What is a founder effect?
A: When a new population is started by a small group, leading to different allele frequencies than the original population.
176
Case Study: Greater Prairie Chickens (GPC)
Why did the GPC population decline?
A: Habitat loss due to farmland conversion—not due to lack of fitness.
177
Q: How was the GPC population recovered? What does this demonstrate?
A: Gene flow was reintroduced by importing chickens from neighboring states. A: Genetic drift due to habitat loss and the importance of gene flow for conservation.
178
Q: What is the Afrikaaners founder effect?
A: 50% of the current 2.5 million population trace back to 20 names from a ship; one-third of white South Africans descend from just 40 founders. Huntington’s disease is abnormally high due to the founder effect.
179
Q: What does gene flow do to a population?
A: It mixes alleles among populations and can significantly impact gene structure through immigration or emigration.
180
Q: What is gene flow composed of?
A: Gene movement + gene establishment.
181
Q: How much gene flow is needed to preserve variation?
A: Not much— even low levels of gene flow can maintain genetic diversity.
182
Q: How far does gene flow typically occur?
A: Over short distances, although rare long-distance dispersal events can maintain genetic diversity.
183
Q: What is natural selection?
A: A process where organisms better adapted to their environment have higher survival and reproductive success.
184
Q: What is evolutionary or Darwinian fitness?
A: The potential relative contribution of an individual to the gene pool of the next generation.
185
Q: How quickly can the effects of natural selection appear?
A: They can be seen after just a few generations.
186
Q: Under what conditions is natural selection seen quickly?
When:
Environmental changes are drastic (e.g., new predator/prey)
Large-scale immigration or removal of maladaptive traits
Significant phenotypic mutation occurs
187
Q: Which microevolutionary force adapts populations to their environment?
A: Only natural selection.
188
Q: Are all microevolutionary forces adaptive?
A: No, forces like drift are non-adaptive and are considered non-Darwinian.
189
Q: What are the three types of natural selection on continuous/polygenic traits?
A: Stabilizing, Directional, and Diversifying/Disruptive.
190
Q: What is stabilizing selection?
A: Selection that favors the central/average phenotype and selects against extremes.
191
Q: What is an example of stabilizing selection?
A: Birth weight in humans or sickle cell heterozygote advantage.
192
Q: What is directional selection?
A: Selection that favors one extreme phenotype over the average or the other extreme.
193
Q: What happens after directional selection stabilizes?
A: Stabilizing selection usually follows once the optimal phenotype is reached.
194
Q: What is diversifying (disruptive) selection?
A: Selection that favors both extremes of a trait and selects against intermediate phenotypes.
195
Q: What is an example of diversifying/disruptive selection?
A: Beak size in Darwin’s finches—small beaks for small seeds, large beaks for large seeds; intermediates compete with both.
196
Q: Why can’t natural selection lead to perfection?
A: Organisms are limited by historical constraints, pre-existing forms, and trade-offs among traits.
197
Q: Does selection create variation?
A: No, it selects from existing random variation.
198
Q: Does natural selection always result in evolution?
A: No, selection can lead to evolution, but they are not the same.
199
Q: What is a species (biological definition)?
A: A group of individuals that can interbreed and produce viable, fertile offspring.
200
Q: What is the morphological species concept?
A: Defines species based on anatomical differences. It’s easy to apply but subjective and vulnerable to convergent evolution.
201
Q: What is the biological species concept?
A: Defines species by reproductive isolation (RIMs). It's based on evolutionary independence but not applicable to fossils or asexual organisms.
202
Q: What challenges the biological species concept?
A: Asexual reproduction and hybrid species like the grolar bear.
203
Q: What is the phylogenetic species concept?
A: Defines a species as the smallest monophyletic group on a phylogenetic tree. It's testable and widely applicable but limited by available phylogenies.
204
Q: What are reproductive isolating mechanisms (RIMs)?
A: Barriers that prevent gene flow between species.
205
Q: What are the two types of reproductive isolation?
A: Prezygotic (before fertilization) and postzygotic (after fertilization).
206
Q: How are non-sexually reproducing organisms classified?
A: Based on morphological and biochemical traits.
207
Q: What are the phases of speciation?
A: Separation → Divergence (via drift, selection, mutation, or gene flow) → RIMs develop → Speciation.
208
Q: What are prezygotic isolating mechanisms?
habitat isolation
Behavioral isolation (e.g., courtship rituals)
Temporal isolation (e.g., mating times like diurnal vs. nocturnal)
Mechanical isolation (e.g., incompatible reproductive structures)
Gametic isolation (e.g., sperm and egg can’t fertilize due to molecular incompatibility)
209
Q: What are postzygotic isolating mechanisms?
Reduced hybrid viability
Reduced hybrid fertility (e.g., mules)
Hybrid breakdown (F1 fertile but F2 infertile or inviable)
210
Q: What is speciation?
A: The process of one species evolving into two or more distinct species due to reproductive isolation and genetic divergence.
211
Q: How can speciation occur?
A: Through genetic isolation (limited gene flow) or genetic divergence (via mutation, natural selection, and drift).
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Q: What are the two types of speciation?
Allopatric speciation: Occurs due to geographic separation.
Sympatric speciation: Occurs without geographic separation.
213
Q: What causes allopatric speciation?
Geographic isolation, followed by mutation, drift, and selection driving divergence.
214
Q: What is dispersal in allopatric speciation?
A: Individuals move to a new location and become genetically isolated (founder effect).
215
Q: What is vicariance in allopatric speciation?
A: A physical barrier splits a habitat, isolating populations.
216
Q: What is an example of vicariance in speciation?
A: Snapping shrimp were separated by the Isthmus of Panama. No gene flow occurred, and they evolved into different species.
217
Q: What is sympatric speciation?
A: Speciation that occurs without geographic separation—species diverge while living in the same area.
218
Q: How does sympatric speciation occur despite no physical separation?
A: Through reproductive isolation within a shared environment, often due to Darwinian fitness or competition for different food sources.
219
Q: What kind of genetic change can drive sympatric speciation?
A: A mutation that results in genetic incompatibility.
220
Q: What is an example of sympatric speciation?
A: Apple maggot flies: originally laid eggs on hawthorn fruit; with the introduction of apples (which ripen earlier), flies adapted to different fruiting times, causing divergence.
221
Q: How does the rate of sympatric speciation compare to allopatric?
A: Sympatric speciation is often slower because gene flow can still occur.
222
Q: How can hybridization lead to sympatric speciation?
A: Through allopolyploidy, where a hybrid offspring has doubled chromosomes from two species and becomes reproductively isolated.
223
Q: What are hybrid zones and ecotones?
A: Transitional areas where species interbreed—e.g., yellow-bellied and fire-bellied toads.
224
Q: What is polyploidy?
A: A condition where an organism has more than two sets of chromosomes.
225
Q: What is autopolyploidy?
A: Multiple chromosome sets derived from one species due to genome duplication.
226
Q: What is allopolyploidy?
A: Polyploidy resulting from the mating of two different species, creating offspring with chromosomes from both.
227
Q: What factors increase the speed of speciation?
A: Prezygotic reproductive isolation mechanisms like polyploidization, behavioral isolation, and allopatry.
228
Q: What factors slow down speciation?
A: Gene flow, high hybrid viability, and sympatric speciation (unless polyploidy is involved).
229
Q: What is phylogenetics?
A: The study of evolutionary relatedness among organisms.
230
Q: What is a phylogeny?
A: The evolutionary history of a group of organisms, shown diagrammatically.
231
Q: What are phylogenetic trees?
A: Diagrams that represent hypotheses about evolutionary relationships.
232
Q: What do the parts of a phylogenetic tree represent?
Nodes = points where groups split
Branches = evolutionary paths
Tips = taxa/endpoints
Trunk = most inclusive, oldest taxon
233
Q: What is a polytomy?
A: A point on a tree where more than two branches diverge—indicates uncertainty in divergence order.
234
Q: Are phylogenetic trees static?
A: No, they are hypotheses and can change with new data.
235
Q: What is a monophyletic group (clade)?
A: A group including a common ancestor and all its descendants.
236
Q: What is a paraphyletic group?
A: A group that includes the common ancestor but not all its descendants.
237
Q: What is a polyphyletic group?
A: An artificial group of distantly related taxa not including their common ancestor.
238
Q: How is a phylogenetic tree constructed?
A: By measuring characteristics (morphological or genetic) and inferring relationships.
239
Q: What are characters in phylogenetics?
A: Traits that inform phylogenies—morphological, behavioral, or molecular (e.g., DNA sequences).
240
Q: What are homologous structures?
A: Traits inherited from a common ancestor (e.g., bat wings and human hands).
241
Q: Why are homologous traits important?
A: They contain genetic similarities and support common ancestry.
242
Q: What are analogous structures (homoplasies)?
A: Similar traits that evolved independently, not from a common ancestor (e.g., insect and bird wings).
243
Q: How do we resolve whether a trait is homologous or analogous?
A: Using fossil evidence or genetic analysis—if the trait is present in a common ancestor, it's homologous.
244
Q: What is phenetics?
A: Classifying organisms based on overall similarity, regardless of evolutionary relationship.
245
Q: What is cladistic analysis?
A: Classification based only on homologous traits, constructing trees based on evolutionary models.
246
Q: Why is cladistic analysis preferred?
A: It is more exact and focuses on shared derived characters (synapomorphies).
247
Q: What is a synapomorphy?
A: A shared derived trait that provides evidence of a relationship between two taxa.
248
Q: What is a basal character (symplesiomorphy)?
A: A trait present in the common ancestor of the group.
249
Q: What is an autapomorphy?
A: A trait that is unique to a single taxon.
250
Q: What is the principle of parsimony in phylogenetics?
A: The most accurate tree is the one with the fewest evolutionary changes.
251
Q: What are molecular phylogenies?
A: Phylogenies built using DNA to trace ancestry and estimate evolutionary time.
252
Q: What is a molecular clock?
A: The idea that mutations accumulate at a steady rate, allowing estimation of evolutionary time.
253
Q: What is an example of a slow-mutating gene used in molecular phylogenies?
A: rRNA genes.
254
Q: What can mtDNA be used for in phylogenetics?
A: Measuring absolute time for recent evolutionary changes.
255
Q: What is homeostasis?
A: A self-regulating process by which biological systems maintain a stable internal environment.
256
Q: What are the 5 steps of homeostasis?
Stimulus produces a change in a variable.
Receptors detect the change.
Input sent to control center (e.g., CNS).
Output sent to effectors (e.g., endocrine or nervous system).
Response restores homeostasis and reduces stimulus.
257
Q: What is an example of homeostasis in action?
A: Thermoregulation—animals detect heat and respond by sweating, panting, or shivering to maintain body temperature.
258
Q: What are endotherms?
A: Organisms (like birds and mammals) that regulate their internal body temperature using metabolic heat.
259
Q: What are heterotherms?
A: Organisms that have a variable body temperature; some insects are spatial heterotherms with different temperatures in body parts.
260
Q: What are homeotherms?
A: Organisms that maintain a relatively constant body temperature, often due to stable environments (e.g., marine fish).
261
Q: What are ectotherms?
A: Organisms that do not regulate internal temperature and rely on the external environment (e.g., reptiles).
262
Q: What is a regulator?
A: An organism that uses internal mechanisms to maintain stability despite external fluctuations.
263
Q: What is a conformer?
A: An organism whose internal conditions change with the external environment.
264
Q: What stores and releases glucose in the body?
A: Liver and muscle tissue store glucose via insulin; glucose is released from glycogen stores during fasting.
265
Q: How do insulin and glucagon affect blood glucose?
Insulin decreases blood glucose.
Glucagon increases blood glucose.
266
Q: How do metabolic needs change in different conditions?
A: In hibernation or ectothermic species, glucose needs are reduced due to decreased metabolic activity.
267
Q: What is allostasis?
A: Stability through change—adjusting internal conditions in response to anticipated or actual changes.
268
Q: What is the difference between homeostasis and allostasis?
A: Homeostasis maintains a stable set point, while allostasis adapts the set point in response to external or internal changes.
269
Q: What is allostatic load?
A: The wear and tear on the body due to prolonged stress and overuse of allostatic systems.
270
Q: What is behavioral allostasis?
A: Immediate behavioral response to internal prediction errors (e.g., eat more when stressed).
271
Q: What is teleological allostasis?
A: The brain anticipates physiological needs and adjusts set points ahead of time.
272
Q: What is diachronic allostasis?
A: Future-oriented behavior based on learning and prediction of internal state changes. ie. the body's response to chronic stress, where it may adapt by increasing cortisol levels over time, or the body's preparation for hibernation in animals.
273
Q: How does the nervous system communicate?
A: Through fast, short-lived electrical signals for rapid responses.
274
Q: How does the endocrine system communicate?
A: Through slower, long-lasting hormonal signals regulating growth, development, and metabolism.
275
Q: What do endocrine glands do?
A: Secrete hormones or neurohormones into body fluids (e.g., blood).
276
Q: What are local regulators?
A: Molecules that act near their site of release and never enter the bloodstream (e.g., interleukins, histamine).
277
Q: What are pheromones?
A: Molecules that leave one organism and act at a distance on another, influencing behavior or physiology.
278
Q: What are prostaglandins (PGs)?
A: Local hormones that influence uterine contractions, pain, fever, and inflammation—targeted by aspirin.
279
Q: What is nitric oxide (NO)?
A: A signaling molecule involved in vasodilation, neurotransmission, and immune response.
280
Q: What is autocrine signaling?
A: A cell signals to itself (e.g., quorum sensing in bacteria).
281
Q: What is paracrine signaling?
A: A cell signals to nearby cells (e.g., neural synapses).
282
Q: What is endocrine signaling?
A: Hormones travel through the bloodstream to act on distant target cells with specific receptors.
283
Q: What are the four main types of hormones based on chemical structure?
A: Amino acid derivatives, proteins/peptides, steroids, and fatty acid derivatives.
284
Q: What are amino acid derivative hormones like adrenaline characterized by?
A: Soluble in blood, stored in vesicles, made by enzymes, bind to plasma membrane receptors, and use second messengers like cAMP.
285
Q: What are protein/peptide hormones?
A: The most common hormone type (e.g., insulin, glucagon), gene-encoded, soluble in blood, bind to plasma membrane receptors, and use second messengers.
286
Q: What are steroid hormones?
A: Lipid-based hormones like testosterone and estrogen; insoluble in blood, released upon synthesis, bind to cytoplasmic receptors, and are derived from cholesterol.
287
Q: What are fatty acid derivative hormones?
A: Hormones like juvenile hormone in insects; receptor location varies.
288
Q: What are the six steps in an endocrine signaling pathway?
Synthesis by endocrine gland
Secretion (regulated or continuous)
Transport (via blood or carrier proteins)
Reception (target cell with specific receptor)
Transduction (signal cascade, often with second messengers)
Response (transient or long-term, like gene expression change)
289
How are hydrophilic and hydrophobic hormones transported in blood?
Hydrophilic hormones float freely; hydrophobic hormones bind to carrier proteins (e.g., albumins).
290
Q: What determines if a cell can respond to a hormone?
A: The presence of the correct receptor.
291
Q: What do agonist and antagonist hormones do?
A: Agonists stimulate a response; antagonists inhibit a response.
292
Q: What happens during signal transduction?
A: Extracellular signals produce effects inside the target cell by altering gene expression, metabolism, or structure via signaling cascades.
293
Q: What is the role of second messengers like cAMP, IP3, and Ca²⁺?
A: To amplify the signal inside the cell and mediate the response.
294
Q: What are protein kinases and their role in signaling?
A: Enzymes that activate or deactivate other proteins through phosphorylation, propagating the signal.
295
Q: What is phosphorylation?
A: A process that turns proteins on or off by adding or removing a phosphate group.
296
Q: What affects a cell’s response to a hormone?
A: Ligand concentration, receptor expression, receptor affinity, and saturation.
297
Q: What dual functions can receptors have?
A: Receptors may act as enzymes, ion channels, or transcription factors.
298
Q: How do most hormones maintain homeostasis?
A: By acting in antagonistic pairs (e.g., insulin and glucagon).
299
Q: How do insulin and glucagon regulate blood glucose?
Insulin decreases glucose by promoting cellular uptake.
Glucagon increases glucose by stimulating liver to release stored sugar.
300
Q: When is insulin released?
A: When blood glucose is high.
301
Q: When is glucagon released?
A: When blood glucose is low.
302
Q: How do animals in cold environments conserve energy?
A: Through hibernation, hypothermia, and reduced glucose needs.
303
Q: What is the relationship between the hypothalamus and the pituitary gland?
A: The hypothalamus is the control center that regulates the pituitary, which stores and releases hormones.
304
Q: What kind of hormones does the hypothalamus produce?
A: Tropic hormones that stimulate the release of other hormones.
305
Q: What is a portal system in the endocrine context?
A: A network where one capillary bed drains into another, used to deliver hypothalamic hormones to the anterior pituitary.
306
Q: What is a tropic hormone?
A: A hormone that triggers the release of other hormones.
307
Q: How is the anterior pituitary controlled?
A: By hypothalamic tropic hormones via a portal system.
308
Q: What type of hormones does the anterior pituitary release?
A: Peptide hormones.
309
Q: How is the posterior pituitary controlled?
A: By neural signals from hypothalamic axons.
310
Q: What is the posterior pituitary considered?
A: An extension of the hypothalamus that stores and releases hormones.
311
Q: What hormones are released by the adrenal glands?
A: Mostly peptide hormones, as well as adrenaline and steroids (like cortisol).
312
Q: What is the HPA axis?
A: The hypothalamic-pituitary-adrenal axis; a major part of the endocrine system controlling stress responses.
313
Q: What is the CRH-ACTH-glucocorticoid pathway?
A: The hypothalamus releases CRH → anterior pituitary releases ACTH → adrenal gland releases glucocorticoids (stress hormones).
314
Q: What kind of hormones are CRH and ACTH?
A: Tropic peptide hormones.
315
Q: How does the adrenal gland release different hormones?
Cortex: Releases hormones for stress (glucocorticoids), salt balance, and sex.
Medulla: Releases adrenaline.
316
Q: What are the 4 functions of the nervous system?
Receive signals
Transmit signals
Integrate and interpret signals
Coordinate a response
317
Q: What does the central nervous system (CNS) do?
A: Acts as the integrator using the brain and spinal cord (neurons and glia); it's powerful but energy-demanding.
318
Q: What does the peripheral nervous system (PNS) include?
A: All neurons and their projections outside the CNS.
319
Q: What do sensory receptors do?
A: Detect environmental signals and send them to the CNS via sensory neurons.
320
Q: What are the main parts of a neuron and their functions?
Dendrites: Receive signals
Cell body: Integrates signals
Axon: Transmits signals
Axon terminals: Communicate with next cells
Myelin sheath: Insulates axons for faster conduction
Nodes of Ranvier: Sites of action potential conduction
321
Q: What are glial cells and their functions?
Microglia: Defense and clean-up
Astrocytes: Nourish neurons and clean extracellular environment
Oligodendrocytes (CNS)/ Schwann cells (PNS): Form the myelin sheath for insulation
322
Q: What is a ganglion?
A: A cluster of neuron cell bodies.
323
Q: What is a reflex arc?
A: The simplest circuit in animals: Sensory → Afferent neuron → Efferent neuron → Muscle (effector)
324
Q: What are the 5 steps in the evolution of nervous systems?
Increase in nerve number
Ganglia formation
Cell function specialization
Complex synaptic contacts
Cephalization
325
Q: What is cephalization?
A: The evolutionary trend of concentrating sensory and neural structures at the head (anterior end).
326
Q: Why is cephalization advantageous?
A: It improves stimulus detection and responses, aiding survival in mobile animals.
327
Q: What animals are cephalized vs non-cephalized?
Cephalized: Humans, dogs, insects
Non-cephalized: Starfish, jellyfish, sponges
328
Q: What is the role of the hindbrain?
A: Controls basic functions like respiration and movement using evolved depolarization patterns.
329
Q: What is the thalamus?
A: Part of the interbrain; coordinates motor functions like walking (central pattern generator).
330
Q: What is the role of the midbrain?
A: Connects to the forebrain and supports more advanced integration.
331
Q: What is the role of the forebrain?
A: Processes complex signals and coordinates advanced responses.
332
Q: What is resting membrane potential in neurons?
A: The electrical difference across a membrane, typically -70 mV (inside more negative).
333
Q: What ions are involved in setting membrane potential?
A: Na⁺, K⁺, Cl⁻, and large anions (A⁻)
334
Q: What happens during an action potential?
Resting at -70 mV
Reaches threshold at -50 mV
Depolarization: Na⁺ channels open, Na⁺ rushes in
Repolarization: K⁺ channels open, K⁺ leaves cell
Hyperpolarization: Too much K⁺ leaves
Restored by Na⁺/K⁺ pump
335
Q: What influences action potential speed?
Axon diameter: Bigger is faster
Myelination: Enables saltatory conduction, making signals jump between nodes
336
Q: What is a synapse?
A: A junction where a neuron communicates with another cell.
337
Q: What are the roles of pre- and postsynaptic cells?
Presynaptic: Sends neurotransmitters
Postsynaptic: Receives and responds
338
Q: What are the 5 classes of neurotransmitters?
Acetylcholine – muscle junctions
Biogenic amines – mood and movement
Amino acids – glutamate (excitatory), GABA (inhibitory)
Neuropeptides – modulate other neurotransmitters
Gaseous – e.g., nitric oxide, used locally
339
Q: What happens when an action potential reaches the synaptic terminal?
Opens Ca²⁺ channels
Vesicles fuse with membrane
Neurotransmitters diffuse across synapse
Bind to postsynaptic receptors → EPSP or IPSP
340
Q: What is an EPSP?
A: Excitatory postsynaptic potential – slight depolarization that makes a neuron more likely to fire.
341
Q: What is an IPSP?
A: Inhibitory postsynaptic potential – hyperpolarization that makes firing less likely.
342
Q: What determines if a neuron fires an action potential?
A: The summation of all EPSPs and IPSPs at the axon hillock.
343
Q: What is required for any sensory system to work?
A: Detection of environmental stimuli through specialized receptors.
344
Q: What are examples of sensory receptors?
Vision: Rods and cones detect electromagnetic signals
Smell: Detects volatile chemicals (neuronal)
Taste: Detects chemicals (non-neuronal)
Touch: Pressure sensing
Hearing: Detects sound waves
Magnetoreception: Detects magnetic fields
345
Q: What are pheromones?
A: Signaling chemicals released into the environment by one sex to attract the other; bind receptors on sensory neurons to trigger signaling pathways.
346
Q: Do humans use pheromones?
A: It's still unclear if humans detect or respond to pheromones.
347
Q: What type of sensory responses are taste and smell?
A: Chemosensory responses involving receptors that bind specific chemicals to induce action potentials.
348
Q: What is unique about taste receptors?
A: They are not neurons but sensory cells with microvilli that detect chemicals.
349
Q: What is unique about smell receptors?
A: They are located on neurons directly.
350
Q: How do bees use magnetosensing?
A: They detect disturbances in flowers’ magnetic fields to avoid “empty” ones.
351
Q: What are magnetite and cytochromes used for in animals?
A: Magnetite helps orient to magnetic fields; cytochromes may enable photo-based magnetoreception.
352
Q: What is the role of cones and rods in vision?
Cones: Detect color.
Rods: Detect brightness (black and white).
353
Q: Where are light detectors located?
A: In the retina; action potentials leave the eye via the optic nerve.
354
Q: What detects external temperature?
A: TRP receptors, which trigger calcium release and depolarization in neurons.
355
Q: What do menthol and capsaicin do?
Menthol: Activates cold receptors.
Capsaicin: Activates hot/spicy receptors.
356
Q: Where is internal body temperature regulated?
A: In the hypothalamus, which controls sweating, shivering, vasodilation, and vasoconstriction.
357
Q: What are the four types of mechanoreceptors?
Merkel's disks
Meissner's corpuscles
Ruffini endings
Pacinian corpuscles
358
Q: What do mechanoreceptors detect?
A: Different types and depths of touch.
359
Q: What is the purpose of internal circulation?
A: Connects cells and organs, exchanges gases, absorbs nutrients, and removes wastes.
360
Q: Which animals have gastrovascular cavities instead of circulatory systems?
A: Hydras, cnidarians, and flatworms.
361
Q: What is an open circulatory system?
A: Blood mixes with interstitial fluid and bathes tissues directly (e.g., arthropods, mollusks).
362
Q: What is a closed circulatory system?
A: Blood is confined to vessels and separate from interstitial fluid (e.g., vertebrates, squid).
363
Q: What are the main components of closed circulatory systems?
Heart: Atria receive blood; ventricles pump it out.
Arteries: Carry blood away from the heart.
Veins: Return blood to the heart.
Capillaries: Site of nutrient/gas exchange.
Lymph vessels: Return excess fluid to the blood.
364
Q: What type of circulation do fish have?
A: Single circulation: One atrium and one ventricle pump blood through gills and body.
365
Q: How does amphibian circulation differ?
A: They have intermediate circulation using lungs and skin for gas exchange; some mixing of blood occurs.
366
Q: What is double circulation (birds and mammals)?
A: Separate pulmonary (lungs) and systemic (body) circuits with 2 atria and 2 ventricles for efficiency.
367
Q: What determines blood flow in capillaries?
A: Cross-sectional area, resistance, and pressure drop to allow time for nutrient/waste exchange.
368
Q: How is blood flow regulated?
A: By vasodilators (increase flow) and vasoconstrictors (reduce flow).
369
Q: What is hemoglobin?
A: A protein in red blood cells that binds oxygen using iron in heme groups; carries 4 O₂ molecules.
370
Q: How do high-altitude birds adapt?
A: They have hemoglobin with a higher O₂ affinity and extra air sacs (e.g., bar-headed geese).
371
Q: What is an immune response?
A: The body’s ability to detect and eliminate foreign macromolecules.
372
Q: What are lymphocytes?
A: Nongranular white blood cells that participate in immune responses.
373
Q: What are antigens and antibodies?
Antigen: A molecule recognized as foreign.
Antibody: A protein produced by B cells that binds antigens.
374
Q: What is innate immunity?
A: Immediate, general defense present at all times; includes barriers, inflammation, and phagocytosis.
375
Q: What are examples of physical barriers?
A: Skin, mucous membranes, and invertebrate cuticles (with chitin).
376
Q: What are cytokines?
A: Signaling proteins that regulate immune cell interactions (e.g., interleukins, interferons, TNF).
377
Q: What is the complement system?
A: Proteins that enhance inflammation, lyse pathogens, and attract white blood cells.
378
Q: What cells perform phagocytosis?
A: Neutrophils and macrophages, which engulf and destroy pathogens.
379
Q: What are natural killer (NK) cells?
A: Immune cells that destroy virus-infected or cancerous cells.
380
Q: What are the hallmarks of inflammation?
Increased blood flow (vasodilation)
Increased capillary permeability
Migration of immune cells to the infection site
Enhanced phagocytosis
381
Q: How does local hyperthermia help the immune response?
A: Increases temperature in a localized area to enhance inflammation and possibly promote a systemic fever.
382
Q: What triggers adaptive immunity?
A: Antigen presentation by macrophages and other APCs.
383
Q: What are the two branches of adaptive immunity?
Antibody-mediated (humoral) immunity
Cell-mediated (cellular) immunity
384
Q: How does adaptive immunity compare to innate immunity?
A: It's slower but more specific and has memory.
385
Q: What are lymphocytes and their two types?
A: White blood cells involved in adaptive immunity:
T cells (cell-mediated) mature in thymus
B cells (antibody-mediated) mature in bone marrow
386
Q: What do cytotoxic T cells do?
A: Kill infected or abnormal cells displaying foreign antigens.
387
Q: What do helper T cells do?
A: Secrete cytokines and activate other immune cells.
388
Q: What do B cells do?
A: Differentiate into plasma cells that secrete antibodies, or memory cells that retain immunity.
389
Q: Why is innate immunity limited?
A: Pathogens evolve quickly and innate immunity has no memory.
390
Q: What are APCs and what do they do?
Antigen Presenting Cells
A: Macrophages, dendritic cells, and B-cells that present foreign antigens via MHCs to helper T cells.
391
Q: How are B cells activated?
Antigen binding
Presentation by APCs with MHC
Helper T cell secretes interleukins
392
Q: What do activated B cells produce?
A: Clones that become plasma cells (secrete antibodies) or memory B cells.
393
Q: What do antibodies do?
Bind antigens
Neutralize pathogens
Trigger agglutination for easier phagocytosis
Activate complement system
Recruit NK cells
394
Q: What are the major antibody classes?
A: IgM, IgG, IgE, IgA, IgD
395
Q: What cells mediate cellular immunity?
A: T cells (mature in thymus)
396
Q: What do cytotoxic T cells do upon activation?
A: Migrate to infected cells and release proteins (e.g. perforin) to kill them.
397
Q: How do T cells recognize antigens?
A: Only when presented on MHC complexes by APCs.
398
Q: What is osmoregulation?
A: Active regulation of water and solute balance to maintain homeostasis and prevent dehydration or swelling.
399
Q: What is the difference between osmolarity, molarity, tonicity, and osmotic pressure?
Osmolarity: Total solute concentration
Molarity: Concentration of a specific solute
Tonicity: Solute effect on cell volume
Osmotic pressure: Water movement force across membrane
400
Q: What does hypertonic mean?
A: Higher solute concentration outside the cell → water exits → cell shrinks.
401
Q: What does hypotonic mean?
A: Lower solute concentration outside the cell → water enters → cell swells.
402
Q: What does isotonic mean?
A: Equal solute concentration → no net water movement.
403
Q: What problem do freshwater fish face?
A: Water flows in → they expel dilute urine.
404
Q: What problem do marine fish face?
A: Water flows out → they drink seawater and excrete excess salts.
405
Q: What is unique about the bull shark?
A: Retains urea + TMAO to maintain high internal osmolarity despite lower salt concentration.
406
Q: What are osmoconformers?
A: Match internal osmolarity to environment (e.g., many marine invertebrates); allostatic.
407
Q: What are osmoregulators?
A: Actively maintain internal osmolarity; homeostatic.
408
Q: What’s the key difference between osmoconformers and osmoregulators?
A: Osmoconformers allow internal change; osmoregulators actively resist change.
409
Q: What is an example of an osmoregulator?
A: Salmon – switch osmoregulation strategy between freshwater and saltwater, regulated by IGF and cortisol.
410
Q: What are the three main processes in urine formation?
Filtration: Blood filtered through glomerular capillaries and Bowman's capsule.
Reabsorption: 99% of filtrate reabsorbed in the proximal convoluted tubule.
Secretion: Additional substances (K⁺, H⁺, NH₄⁺) secreted into distal tubules
411
Q: What is the nephron?
A: The functional unit of the kidney responsible for filtering blood and forming urine.
412
Q: What is the role of the Loop of Henle?
A: Establishes an osmotic gradient used for water reabsorption in the collecting duct.
413
Q: What is the pathway of filtrate through a nephron?
A: Renal artery → Glomerulus → PCT → Loop of Henle → DCT → Collecting duct → Ureter → Urethra → Out.
414
Q: What is the RAAS system and its role?
A: Renin-Angiotensin-Aldosterone System raises blood pressure through vasoconstriction and salt/water reabsorption.
415
Q: How does RAAS respond to low blood pressure?
Kidney releases renin
Renin converts angiotensinogen → angiotensin II → vasoconstriction
Angiotensin II triggers aldosterone release, increasing Na⁺ reabsorption → water follows → BP increases.
416
Q: What does ADH do?
A: Released by the posterior pituitary; increases water reabsorption by opening pores in the collecting duct.
417
Q: How are kangaroo rats adapted to dry environments?
Nocturnal behavior
Select water-rich food
Longer Loop of Henle
High ADH levels to retain water
418
Q: What is the benefit of sexual reproduction?
A: Genetic variation and masking of harmful alleles.
419
Q: What is the benefit of asexual reproduction?
A: Efficiency—no mate needed, preserves good gene combos.
420
Q: What are examples of asexual reproduction?
Parthenogenesis (e.g., some sharks)
Budding (e.g., corals)
Fragmentation (e.g., annelid worms)
421
Q: What is the bird sex chromosome system?
A: ZZ = male, ZW = female
422
Q: What are the human sex chromosomes?
A: XX = female, XY = male
423
Q: What is environmental sex determination?
A: In some reptiles, sex is determined by egg incubation temperature (affected by climate change).
424
Q: What is population-based sex change?
A: Some fish (e.g., parrotfish) change sex depending on male-to-female ratio.
425
Q: What is ploidy in insects?
A: Males are haploid, with one set of chromosomes.
426
Q: Define ovipary.
A: Egg laying; development occurs outside the mother (e.g., birds).
427
Q: Define ovovivipary.
A: Embryo develops inside the female but nourished by yolk (e.g., sharks).
428
Q: Define vivipary.
A: Embryo develops inside the mother and is nourished directly (e.g., mammals).
429
Q: What hormone pathway regulates vertebrate reproduction?
Hypothalamus → GnRH → Anterior Pituitary → LH & FSH → Gonads → Sex hormones
430
Q: What does AMH do?
A: Anti-Müllerian Hormone suppresses female structures and promotes male development.
431
Q: What does the gene CYP19A1 do?
A: Converts testosterone to estradiol; critical for female development.
432
Q: What is a blastula?
A: A hollow ball of cells formed after cleavage; contains inner cell mass and trophoblast.
433
Q: What are the three germ layers formed during gastrulation?
Ectoderm → Skin and nervous system
Mesoderm → Muscles
Endoderm → Internal organs
434
Q: What does the trophoblast become?
A: Structures like the placenta.
435
Q: What are sneaker males?
A: Males who avoid direct competition and sneak in to mate.
436
Q: Why are sneaker males relevant to mate choice?
A: They show alternative mating strategies can succeed, even without dominance.
437
Q: What is negative frequency-dependent selection?
A: A rare trait is more successful, but loses its advantage when common.
ie A: Sneaker success declines as they become more common—maintains diversity.
438
Q: What are the main costs of sexual reproduction according to Maynard Smith?
A: Energy to find mates, risk of STIs and predation, reduced relatedness to offspring (50%), disruption of good gene combinations, and competition for mates.
439
Q: What are the main benefits of sexual reproduction?
A: Genetic variation, shared investment of gametes, potentially more or more successful offspring.
440
Q: Under what condition is sex favored evolutionarily?
A: Only if the benefits outweigh the costs—e.g., producing more or more successful offspring.
441
Q: What is Muller's Ratchet and how does sex help avoid it?
A: In asexual reproduction, harmful mutations accumulate; sexual reproduction can reduce mutational load and increase exposure to beneficial mutations.
442
Q: What did Williams argue about genetic diversity?
In uncertain environments, diversity is favored:
In time → use sex
In space → disperse genetically diverse offspring
443
Q: When is sex favored in some species like Daphnia?
A: During stressful environments; otherwise, they reproduce asexually to avoid the costs of mating.
444
Q: What is sexual dimorphism?
A: Physical or behavioral differences between males and females, often due to differing reproductive strategies.
445
Q: What is intrasexual selection?
A: Competition among males for mates (e.g., rutting elk).
446
Q: What is intersexual selection?
A: Female choice for advantageous male traits.
447
Q: What are direct benefits of mate choice?
A: Tangible gains like food or resources (e.g., sexual cannibalism).
448
Q: What are indirect benefits of mate choice?
A: Genetic advantages, like better immune genes or compatible traits.
449
Q: What are sneaker males?
A: Males that avoid direct competition and sneak in to mate.
450
Q: How do bluegill sunfish show alternative male strategies?
A: Parental males guard nests, sneaker males dart in to fertilize eggs, and satellite males mimic females.
451
Q: Why are sneaker males relevant to mate choice?
A: They show successful alternative strategies and challenge dominance-based mating.
452
Q: What is negative frequency-dependent selection?
A: A rare trait has higher fitness but loses advantage as it becomes common.
453
Q: How does this apply to sneaker males?
A: Sneaker males succeed when rare, but become less effective when common, keeping strategy diversity balanced.
454
Q: Are behaviors subject to natural selection like physical traits?
A: Yes, behavioral traits can evolve and be selected for if heritable.
455
Q: What are fixed action patterns?
A: Genetically determined, heritable behavioral responses to specific stimuli (e.g., migration triggered by cold).
456
Q: What are examples of physical communication?
A: Fruit fly mating: orienting, tapping, singing.
457
Q: What are examples of chemical communication?
A: Gypsy moths (pheromones), cross-species pollination signals.
458
Q: What are the four types of social interactions and their fitness outcomes?
Spite: -/- (disfavored)
Selfishness: +/- (favored)
Altruism: -/+ (costly to actor)
Cooperation: +/+ (favored)
459
Q: What is inclusive fitness?
A: Total fitness including own reproduction plus helping relatives reproduce.
460
Q: What is Hamilton's Rule?
A: Altruism is favored if RB > C, where R = relatedness, B = benefit, C = cost.
461
Q: How do ground squirrels demonstrate altruism?
A: Females call to warn kin, even though it increases their risk—example of kin selection.
462
Q: What is eusociality in hymenopterans (bees/wasps)?
A: One queen reproduces; diploid females sacrifice reproduction to help relatives, driven by high relatedness.
463
Q: Why do female hymenopterans benefit more from helping sisters?
A: Sisters share 75% of genes (haplodiploidy), more than with their own offspring.
464
Q: What is reciprocal altruism?
A: Helping non-relatives with expectation of future help (e.g., vampire bats share food).
465
Q: What makes reciprocity work?
A: Memory of the event and enforcement mechanisms.
466
Q: What is organismal ecology?
A: Study of how individual organisms interact with their environment.
467
Q: What is ecosystem ecology?
A: Study of interactions between living communities and abiotic environmental factors.
468
Q: Define landscapes, biomes, and biospheres.
Landscape: Assemblage of ecosystems
Biome: Large-scale ecosystem type in a geographic area
Biosphere: All ecosystems on Earth
469
Q: What are the three key variables of a population?
A: Size, density, and dispersion.
470
Q: What are the types of dispersion?
Clumped: Limited resources, offspring stay near birth.
Uniform: Even resources, competition.
Random: Uncommon; due to many abiotic/biotic factors.
471
Q: What is carrying capacity (K)?
A: The maximum population size an environment can support.
472
Q: Why does realized growth rate (r) decrease as N approaches K in logistic growth?
A: Due to density-dependent factors like competition, disease, and predation.
473
Q: What are density-independent factors?
A: Birth/death rates unaffected by population density.
474
Q: Characteristics of r-strategists?
A: Short lifespan, early reproduction, many offspring, no parental care.
475
Q: Characteristics of K-strategists?
A: Long lifespan, late reproduction, few offspring, parental care.
476
Q: What are the three survivorship curve types?
Type I: Low early mortality (e.g., humans)
Type II: Constant mortality (e.g., birds)
Type III: High early mortality (e.g., fish, insects)
477
Q: What is semelparity?
A: Single reproductive event (e.g., salmon)
478
Q: What is iteroparity?
A: Multiple reproductive events (e.g., ducks)
479
Q: What two structures help predict population growth?
A: Age structure and sex ratio.
480
Q: What does the lynx-hare case illustrate?
A: Population cycles driven by predation and stress-induced lower reproduction in hares.
481
Q: What is an ecological niche?
A: The total of biotic/abiotic conditions a species needs to survive.
482
Q: What is the difference between a fundamental and realized niche?
Fundamental: Potential niche under ideal conditions.
Realized: Actual niche accounting for interactions with other species.
483
Q: What is the competitive exclusion principle?
A: Two species with identical niches cannot coexist; one will outcompete the other.
484
Q: How is competition resolved between species?
A: Through resource partitioning or character displacement.
485
Q: What is character displacement?
A: Evolutionary changes in traits due to competition.
486
Q: What did sticklebacks show about niche evolution?
A: In lakes, marine invasions drove niche specialization through character displacement.
487
Q: What is coevolution?
A: Reciprocal evolutionary change between interacting species (e.g., predator-prey, host-parasite).
488
Q: What’s the difference between Batesian and Müllerian mimicry?
Batesian: Harmless mimics harmful.
Müllerian: Multiple harmful species evolve similar warning signals.
489
Q: What is a keystone species?
A: A species with a disproportionately large impact on community structure (e.g., sea otters and kelp forests).
490
Define mutualism
two or more organisms interact benefiting each other
491
define ammensalism
one has no effect the other is negative
492
define commensalism
one organism benefits from another without affecting it
birds eating off a wildebeest
pollination
493
Q: What is ecological succession?
A: The change in species composition following a disturbance.
494
Q: What is primary succession?
A: Starts from lifeless areas—no soil present.
495
Q: What is secondary succession?
A: Occurs when soil remains after disturbance; faster recovery.
496
Q: What types of species colonize first?
A: r-strategists; later replaced by K-strategists.
497
Q: What are autotrophs and heterotrophs?
Autotrophs: Produce own food (primary producers).
Heterotrophs: Consume others (consumers).
498
Q: Why are food chains short?
A: Only ~10% of energy is passed to the next trophic level.
499
Q: What is the role of decomposers in ecosystems?
A: Recycle nutrients by breaking down organic matter.
500
Q: What are limiting factors in ecosystems?
A: Abiotic (light, water, nutrients) and biotic (prey, predator density).
501
Q: How does carbon cycle through ecosystems?
Photosynthesis captures CO₂.
Respiration and decomposition release it.
Combustion of fossil fuels adds excess CO₂.
502
Q: What is cultural eutrophication?
A: Over-nutrification of water due to human activity, leading to algal blooms and oxygen depletion, light blockages in ocean overall impacts ecosystem
503
Q: What is bioaccumulation vs. biomagnification?
Bioaccumulation: Build-up of toxins in an organism.
Biomagnification: Increase in toxin concentration up the food chain.
504
