Midterm Flashcards
1
Q
What are some threats to biodiversity?
A
1) Resource exploitation
2) Conversion of land
3) Pollution
4) Transport of species
5) Global climate change
2
Q
What are some direct values of biodiversity?
A
1) Pharmaceuticals
2) Food
3) Spices
4) Perfumes
3
Q
What are some indirect values of biodiversity
A
1) Biogeochemical cycles
2) Nutrient cycling
3) Water cycle
4) Prevents soil erosion
5) Regulates climate
6) Ecotourism
4
Q
What are the levels of biodiversity?
A
1) Atoms
2) Organelles
3) Cells
4) Tissues
5) Organs
6) Organisms
7) Populations
8) Communities
9) Ecosystems
10) The Biosphere
5
Q
What is a theory?
A
Theories are unifying explanations of the natural world
6
Q
What is the difference between a theory and hypothesis?
A
Theories have withstood rigorous scientific testing, challenge and debate.
7
Q
What is the difference between ultimate and proximate questions?
A
- Ultimate: Concerned with evolutionary origins and functions
- Proximate: Deal with mechanisms and don’t always require evolutionary explanations
8
Q
What are the characteristics that define life?
A
1) Reproduction
2) Growth
3) Metabolism
4) Evolves
5) Responds to stimuli
6) Homeostasis
9
Q
How do you test for these characteristics?
A
1) Fecundity & Offspring
2) Change in mass, length
3) Consumption, CO2, O2, waste output
4) Change in DNA or genetics over time
10
Q
What is the Scala Naturae?
A
It was a scale created by Aristotle to classify all life on Earth. It was organized by complexity and was based on the idea that species are fixed.
11
Q
What is nomenclature?
A
A system of rules for naming things
12
Q
What is taxonomy?
A
The practice of naming and classifying organisms
13
Q
What is systematics?
A
The theory and practice of classifying organisms based on evolutionary history (phylogeny).
14
Q
What are the 3 problems that arise from common names?
A
1) Different names for the same species
2) Same name for different species
3) Common name may imply relationships that don’t exist
15
Q
Who created the Linnean system?
A
Carolus Linneas
16
Q
What are the 3 properties of the Linnean system?
A
1) Use of Latin as a universal language of scientific nomenclature
2) Use of unique binomen as name of each species
3) Classify and group species usin hierarchial categories based on relatedness/and or similarity
17
Q
What is a binomial name comprised of?
A
A binomial name has 2 parts: a genus and a specific name
18
Q
What are phylogenetic trees?
A
Evolutionary trees that shows the evolutionary relationship between organisms (past or present): between common ancestors and descendants.
- They are hypotheses for evolutionary relationships.
19
Q
What is the goal of phylogenetic trees?
A
Organize species into groups with common ancestry
20
Q
What is a taxon?
A
Named group at any level of classification
21
Q
What is a clade?
A
A valid group includes the ancestor at any node and everything beyond it (descendants).
22
Q
How are relationships among taxa interpreted?
A
By order in which the branches split.
23
Q
What is an in-group?
A
Group whose relationships that we are interested in untangling.
24
Q
What is an out-group?
A
One or more taxa that are distantly related to the in-group, but diverged from it at an earlier time.
25
What are some examples of information that systematists collect to build phylogenetic trees?
1) Morphology
2) Behaviour
3) DNA
4) Biochemistry
26
What is a character?
Type of structure, behaviour, DNA sequence etc.
27
What is a state?
A state is a manifestation of a character.
28
What is the principle of parsimony?
Construct a set of nested relationships that minimizes the number of times a character changes states.
29
How does the principle of parsimony apply to phylogenetic trees?
Choose a phylogeny that requires the fewest number of evolutionary events because it is more probable.
30
What is an event?
A change in state
31
What are the seven steps of building a cladogram?
1) Enter information into a character state matrix
2) Each state is coded as a number
3) Outgroup states are set at 0 and are considered to be ancestral (original) states
4) If a state is different than in outgroup it is coded as 1 and sid to be derived.
5) Determine a set of nested relationship that minimize the amount of evolutionary changes.
(0-->1, ancestral to derived, 1-->0, derived reverts to ancestral)
6) Start with traits most shared and work from bottom of tree
7) Put traits on the tree first, then the species.
32
When would we have a state where 1-->2?
If there were more than 2 character states
33
What is character state polarization?
When the direction of changes in the character is decided (ex. 0--> 1)
34
What is a synapomorphy?
- A shared, derived state
35
What is a symplesiomorphy?
A shared, ancestral state.
36
What is the difference between homologous and analogous character states?
Homologous: Look the same and have the same evolutionary origin
Analogous: Appear the same but actually evolved independently (convergent evolution)
37
How does molecular phylogenetics work?
1) Matching of bases in selected gene sequences
(4 character states at each locus)
2) Mutations can cause changes in bases
3) Changes accumulate over evolutionary time
4) More matches between species--> more likely to be closely related
38
What is the difference between monophyletic, polyphyletic and paraphyletic groups?
Monophyletic: Contains a common ancestor and all of its descendants and no oter unrelated taxa.
Polyphyletic: Taxa get lumped together even though they do not share common ancestors
Paraphyletic: Groups do not contain all of the common ancestor's descendants.
39
What are the 3 causes of polyphyletic groups?
1) More than one common ancestor
2) Lacking common ancestor that unites members in group
3) Incorrectly grouped by superficial characteristics
40
What is an example of a polyphyletic group?
Bats & Birds --> They are not directly related, they are a product of convergent evolution and have analogous characteristics.
41
What causes a paraphyletic group?
The removal of taxa that are highly divergent from the rest of the clade
42
What was the pre-Darwinian view of evolution?
- Others noted that fossil organisms often did not resemble living ones.
- Thus the extinction of species must occur
43
What were 4 reasons (pre-Darwinian) that explained extinction?
1) Natural disasters/catostrophism (Cuvier)
2) Apparent disappearance of species was actually one species slowly turning into another
3) Supernatural disasters
4) Not actually extinct, just hiding
44
What was Cuvier's hypothesis?
1. Species do not change, they are fixed.
2. The succession of life in Earth's strata is due to catastrophes. These catastrophes cause local extinctions which lead to the fossil presence in the strata.
3. After the catastrophe, new species moved into the area.
45
What was Lamarck's hypothesis?
- Species change over time (evolution) due to the inheritance of acquired characteristics.
- He believed that use/disuse of a structure led to heritable change.
- Traits acquired by an individual during their lifetime would be passed on to their offspring.
46
(True or False) Darwin wrote about the survival of the fittest in On the Origin of Species.
False- He wrote about descent with modification but not survival of the fittest.
47
Why are islands important to understanding biodiversity?
- Islands were key to Darwin's understanding of evolution:
- Finches on different islands were different, but related.
- Redundant forms from one place to another (common ancestry)
- Variation on a basic form within a region (due to "descent with modification")
48
How did Darwin come to the conclusion of descent with modification with his finches?
1. They were dissimilar in critical ways
| 2. Varied in their use of the habitat and way of feeding
49
What were Darwin's 5 observations?
1. Organisms produce many more offspring than survive to reproduce themselves
2. Most populations are relatively stable
3. Resources are limited
4. Variation among individuals within species
5. Some variation is heritable
50
What 3 inferences arise from Darwin's observations?
1. Organisms must compete for these limited resources and not all succeed.
2. Some heritable variations are likely to provide individuals with a competitive advantage
3. Individuals with advantageous variations are likely to leave more offspring than individuals without these variations
51
How does descent with modification work?
1. More individuals with that variation will be present than in the previous generation (This provided a logical mechanism by which natural forces can sleect for advantageous variations).
2. The result is adaptive changes over generations
52
What does descent with modification tell us about how species change over time?
1. The process of natural selection gives rise to adaptations
2. As populations adapt to different environments, new species may arise over many generations
3. Populations evolve, not individuals.
4. Natural selection acts on existing variation
5. Natural selection is context-dependent (no innate tendency toward perfection)
53
What are the 3 types of variation that are considered phenotypic?
1. Form
2. Function
3. Behaviour
54
What is genotypic variation?
Variation in genetic make-up
55
What is the relationship between variation and NS?
For natural selection to act on variation, it must be seen by the environment (expressed in the phenotype) and be heritable (caused by genotype)
56
What are the 4 sources of variation?
1. Mutations - random changes in DNA
2. Recombination (crossing-over)
3. Independent assortment of chromosomes
4. Fertilization (sexual reproduction)
57
What is a selective agent?
Component of natural environment that consistently causes different survival and/or reproduction.
58
What is selective pressure?
The intensity with which the selective agents acts on a population to evolve.
59
What are the two types of selective pressure?
1. Biotic (Predator, disease, competitors)
| 2. Abiotic (Temperature, rainfall)
60
How does natural selection lead to adaptation?
1. Heritable variation: Individuals vary in their characteristics (phenotype) due to varied genetic makeup (genotype)
2. Resources are limited: populations produce more offspring than environment can sustain
3. Some phenotypes, with favorable traits, will be better suited to survive and reproduce (more than others). Their genetic contribution to the next generation is greater, so they are said to have increased fitness.
4. Over time, these characteristics and the genes coding for them of fit individuals will increase over time.
- ---> Adaptation
61
What is the evidence for evolution?
- Evolution is suppored by an overwhelming amount of scientific evidence
- Four data types that document the pattern of evolution are:
- The fossil record
- Homology
- Direct observation
- Biogeography
62
How does the fossil record provide evidence for evolution?
1. Dating of sedimentary rock layers (strata) allows fossils to be placed in time
2. Consistent forms occur in the same aged sediment (stratum)
3. Intermediate forms can be identified that appear to be ancestors of current species
4. Extinction is seen in the record.
63
How do homologous characters provide evidence for evolution?
1. Comparative embryology - A common structure is evidence that the organisms are related
2. Vestigial structures and embryology
3. Vestigial structures
4. Molecular evidence (DNA--> amino acids --> protein)
64
How do direct obesrvations provide evidence for evolution?
- Artifical selection: Breeding selects for desriable phenotypes
- Antibiotic Resistance
- pesticide resistance
65
How does biogeography provide evidence for evolution?
- Regions with "identical" climate have different spp (but show convergence of form and function).
- Geographic barriers often associated with differences in taxonomic groups
- Within a region, organisms are often closely related even across environmental gradients
66
What is a gene?
Combination of two alleles in diploid individuals. One allele per chromosome.
67
What is genetic variation?
The diversity of alleles within a population.
| - Often measured by determining proportion of heterozygotes or # of alleles at various loci.
68
What is phenotype variation?
Variety in visible expression of "types"
| - Can be "types" - male/female
69
What is statistical variation?
Statistical variation is the measure of difference from the central tendency.
70
What is evolution?
Change in the frequencies of alleles in a population (gene pool) between generations.
71
What are the 5 factors that change allele frequency?
1. Natural selection
2. Sexual selection
3. Mutations
4. Gene flow
5. Genetic drift
72
How does sexual selection impact allele frequency?
Increases or decreases the probability that a specific individual will mate
- due to preferred phenotype, inbreeding etc.
- may decrease genetic variation
73
How do mutations impact allel frequency?
- Mutations are a change in an individual's DNA. They can be caused by an error in DNA replicationor a structural damage to DNA.
- Mutations are random
- -> The environment does not cause the right mutations to exist.
- Mutations can be good, bad or neutral (current situation)
74
What is the Lederburg experiment?
1. Sterile velvet is pressed on the grown colonies on the master plate.
2. Cells from each colony are transferred from the velvet to new plates
3. Plates are incubated
75
How does gene flow impact allele frequency?
1. Gene flow is the transfer of genes (alleles) between populations (example interbreeding, migration)
2. Variation WITHIN a population is increased
3. Variation BETWEEN populations is decreased.
76
How does genetic drift impact allele frequency?
- Changes in allele frequency due to chance (regardless of natural selection)
- Allele frequencies "drift" from one generation to the next.
- The impact of drift is greater in smaller populations
- Examples: the bottleneck effect and the founder effect
77
How does the founder effect impact allele frequency?
Founder effect: New population established by a few colonizers.
- Small fraction of the total genetic variation compared to the ancestral population and change in allele frequency.
78
How does the bottleneck effect impact allele frequency?
- A catastrophic event occurs leaving only a few survivors
- The survivors reproduce in the next generation
- Gene frequency in the next generation is different than in the previous generation.
- Rare alleles are more likely be lost due to drift
79
What are the 3 mechanisms of natural selection?
1. Directional Selection
2. Disruptive Selection
3. Stabilizing Selection
80
How does directional selection impact allele frequency?
1. Extreme phenotype is favoured (highest fitness)
2. Response to steady change in the environment
3. Frequency distribution of allele shifts. This can cause loss of allelic varieties (loss of genetic variaton)
4. Directional shift occurs in the mean of the population
81
How does disruptive selection impact allele frequency?
1. Extremes are favoured
2. Results in polymorphism
3. Maintains genetic variation
82
How does stabilizing selection impact allele frequency?
1. Intermediate or common phenotypes are favoured
2. Selection against extremes - eliminates harmful mutations
3. The mean of the population stays the same (variance decreases)
4. Little or no evolutionary change (maintains genetic variation
83
What is negative frequency dependent selection?
A rare genotype has advantage
84
What is an example of heterozygous advantage?
The sickle cell trait in Africa. If people were homozygous for sickle cell trait would die from sickle cell disease. People who were homozygous normal, they would die from malaria. People who were heterzygous for the sickle cell trait would survive due to being immune to both.
85
What are 4 reasons that natural selection cannot fashion perfect organisms?
1. Selection can only on EXISTING variations
2. Evolution is limited by historical constraints
3. Adaptations are often compromises
4. Chance, natural selection and the environment can interact.
86
What is the difference between microevolution and macroevolution?
Microevolution: Evolution at the population level - occurs mainly through selection (which results in adaptation) or drift.
Macroevolution: Evolution change above species level
- origin of complex novel characters
- appearance of higher taxa (phyla)
- mass extinctions
- speciation
87
What is biology's concept of a species?
A species consists of a group of actually or potentially interbreeding individuals that are reproductively isolated from other such groups.
88
What are four flaws in the biological species concept?
1. Only applies to sexually reproducing species - asexual species
2. Suggests that 2 different species would never mate and produce offspring - successful hybrids
3. Ecological species concept: Species is a set of organisms adapted to a particular set of resources called a niche, in the environment. (At extremes of distribution, "species" differs.
4. Phylogenetic species - Evolutionary history (some populations are more unique than the rest).
89
What issue arises with fossil species?
- Can't breed them or observe behaviour
90
What is reproductive isolation?
Isolating mechanisms are required to maintain reproductive isolation between populations.
- Two types: pre-zygotic and post-zygotic isolation
91
What are the 5 types of pre-zygotic isolation?
1. Ecological (habitat) selection
2. Temporal Isolation (Different time of day/season)
3. Behavioural isolation (courtship patterns/pheromones)
4. Mechanical isolation (anatomically incompatible)
5. Gamete isolation (sperm and egg cannot fuse)
92
What are the 3 types of post-zygotic isolation?
1. Zygote death
2. Hybrid infertility - Offspring can't reproduce
3. Hybrid inviability - lower fitness (survival &/or reproduction)
93
What is speciation?
Speciation is the formation of new and distinct species in the evolution.
94
What is the difference between cladogenesis and anagenesis?
Cladogenesis: The branching or splitting of a lineage
Anagenesis: Evolutionary change within a lineage, resulting in differences between sister lineages.
95
What is allopatric speciation?
The first step toward reproductive isolation happens when a single population becomes subdivided by a geographical barrier(s).
96
What is sympatric speciation?
- Subgroups can emerge from a continuous habitat. If individuals in the group stop mating with individuals of a larger population, they may eventually form a new species.
97
How do species become reproductively isolated?
1. A single population becomes subdivided (geogrphically/physically or within a habitat)
2. More likely to mate with individuals in their subgroup, gene flow is greatly reduced (pre and/or post-zygotic isolation)
3. Meanwhile, microevolution (natural selection, genetic drift, mutation, non-random mating) is INDEPENDENTLY working on the subgroups.
4. The separated groups eventually evolve and adapt to their local environment - becoming so different in form, physiology, behaviour, that mating no longer occurs between them --> reproductive isolation!
5. Speciation event has occured.
98
What are hybrids?
Hybrids are individuals formed by mating between unlike forms, usually genetically differentiated populations and species.
- If hybrid individuals are less viable or less reproductively successful than non-hybrid individuals, the two species are considered to be distinct
99
What are the 3 outcomes of the hybrid zone?
1. Stability: Fit hybrids continue to be produced
2. Fusion: Reproductive barriers weaken until 2 species become one.
3. Reinforcement: Hybrids are less fit than either purebred species
100
What is introgression?
1. Incorporation of genes from other species into gene pool.
101
How does the reinforcement of reproductive barriers work?
1. Natural selection reinforces reproductive isolating mechanisms
2. When two populations come back into contact:
- If reproductive isolation is complete --> Speciation
- If it is incomplete --> hybrids
3. If the hybrid has lower fitness than either parental form, selection would act to increase the reproductive isolation.
4. Natural selection favours genes that cause individuals to avoid mating with hybrids (increasing reproductive isolation) --> Speciation
102
What is gradualism?
- Gradualism: Slow differentiation by natural selection over many generations.
103
What is punctuated equlibrium?
- Speciation happens rapidly, followed by relatively long periods of stasis (No change).
104
What are the important events in the history of life?
1. Formation of Earth (4.5 BYA)
2. Life Begins
3. Prokaryotic cells
4. Photosynthesis (cyanobacteria) --> Oxygen in atmosphere
5. Eukaryotic cells
6. Colonization of land
7. Humans
105
Why is the fossil record important?
- It provides evidence of how life has changed over time
- Fossil = preserved remnant/evidence of organisms that lived in the past.
- Associated with sedimentary rocks
- rocks formed through accumulation of mud, silt or sand
- distinct layers of rock are called strata
106
Explain the bias in the fossil layer?
An organism is more likely to be fossilized if:
- hard-bodied than soft-bodied
- aquatic than terrestrial
- inshore marine than offshore
- decomposing organisms absent
107
What is relative dating?
- Relative dating:
- Also known as sedimentary stratigraphy
- -> strata= layer, graph = write, record
- Can't tell how long ago fossil was created
- But can tell which fossil came 1st, 2nd, 3rd etc.
108
What is absolute/radiometric dating?
- Radioactive isotopes in fossils of rocks.
- Decay from one isotopic form to another at a constant rate
Example: Carbon-12 and Carbon-14
- Plants take up C-12 and C-14 during photosynthesis, animals get by eating plants
- C-12 very common: accumulates while living, unchanged after death
- C-14 is rare: begins to decay at the time of death--> becomes nitrogen-14.
109
What does half-life mean?
Half-life is 50% of atoms in a given amount of radioactive substance have decayed.
Ex: Uranium 238 - 4.46 BY, Carbon-14: 5730 years
110
What is continental drift?
- Land masses drift around on plates 'floating' on hot mantle
- Tectonic boundaries are the sites of earthquakes and volcanoes
- Relative locations of land-masses have changed over time
111
What evidence do we have of continental drift?
- Fossils provided the first evidence of continental drift. (Eg Same genus of fossil plant found in Australia, Antarctica and South America - Gondwana)
112
What were the consequences of continental drift?
1. Changes to the environment and climate
2. Opportunities for diversification of life
3. Mass extinctions
113
What happened before life began?
1. Surface began to cool
2. Solid rocks floated on the molten magma
3. Steaming gasses from cooling rock formed an atmosphere lacking oxygen
4. Temperatures dropped - gasses condensed and rained down.
5. Basins filled with water and formed transient oceans
114
When did life begin?
- Stromatolites (3.5 BYA)
- Rocks with a distinctive layer structure
- Look identical to living mats of microbes
- Layers of microbes and sediment
- Top layer uses photosynthesis
- Lower level uses top layer's byproducts
115
How did life originate on Earth?
1. Abiotic synthesis of organic molecules
2. Abiotic synthesis of macromolecules
3. Formation of protocells
4. First nucleic acids
116
How did abiotic synthesis of organic molecules occur?
Inorganic atomospheric gasses (such as methane, ammonia, and hydrogen) react with energy (which can come from asteroid collisions, deep sea hydrothermal vents, lightning) to form organic molecules (lipids, amino acids, nitrogen bases, sugars)
117
What is Miller's experiment?
- In the 1950's, experiments tried to replicate conditions thought to exist BYA
- water vapor, hot seas
- ammonia and methane in atmosphere
- frequent lightning
- Researchers were able to create amino acids.
- > Can't reproduce the exact conditions of early Earth, but large macromolecules can be synthesized in vitro from inorganic molecules
118
How did the abiotic synthesis of macromolecules occur?
Amino acids, Nitrogenous bases, sugars became proteins, enzymes and nucleic acids.
- RNA monomers were produced spontaneously from simple molecules.
- Experiments: Polymers of small organic molecules produced by combining amino acids/nucleotides on hot clay, rock or sand.
119
How did we arrive at the hypothesis for protocells?
- Life reproduces: DNA molecules carry genetic information
- Life requires energy: Metabolism
- Needs to separate itself from environment:
- Cell membrane
- But free floating amino acids, proteins and nucleic acids would not have been able to behave live cells.
120
How were protocells similar to cells today?
- Spontaneous formation of hollow lipid vesicles suggest how early cell-like structures may have arisen.
- Bi-layered structure similar to cell membranes
- Sphere would have been able to export or keep its own products:
- Confining organic molecules increses rate of reactions
- Encourages evolution of cooperative relationships
- Vesicles form faster in the presence of a type of volcanic clay
121
How did the first nucleic acids originate?
- First genetic material: RNA
- single-stranded, fragile, self replicating
- form different shapes depending on environment
- can catalyze many different reactions
- favoured by natural selection --> "RNA world"
- Genetic material of all living organisms today: DNA
- deoxyribonucleic acid
- double helix: paired strands twist around each other
- very stable structure
- more accurately replicated (also favoured by Natural Selection)
122
Where did life originate?
- Hot, mineral-rich deep-sea vents
- where many of the earliest derivative prokaryotes (Archaea) still live.
- Experiments mimicking characteristics of underwater volcanoes produce more amino acids than those not mimicking them.
123
What are three alternate theories to the origins of life?
1. Spontaneous creation = Abiogenesis
- early catalysts (clay or thermal vents)
2. Extraterrestrial origins
- Panspermia (seeds everywhere)
- ET Transplant
3. Special Creation
- Creationism & Intelligent design
