Exam 3 Flashcards
(223 cards)
1
Q
Sensory neurons
A
A nerve cell that detects internal/external stimuli (e.g., touch, temperature, light) that carries sensory signals (electrical signal) to the CNS
2
Q
Interneurons
A
A neuron that passes signals from sensory neurons to motor neurons (in CNS)
3
Q
Motor neurons
A
A nerve cell that carries signals from the central nervous system to effector cells in a muscle/ gland
4
Q
Is the inside of the cell more negative or positive?
A
Inside of cell is generally more negative bc lots of negative proteins
5
Q
Depolarization
A
when neuron becomes more positive, (Na+ enters cell, needs protein channels
6
Q
Re-polarization
A
Cell/Neuron becomes more negative (K+ leaves, needs protein channels
7
Q
How is electrical info transmitted in neurons?
A
as a series of action potentials along the axon over time
8
Q
Action potential
A
Brief electrical signal that travels along a nerve cell (neuron) or muscle cell, allowing it to send information quickly over long distances.
9
Q
What are the main parts of an action potential? (Electrical Info)
A
Resting State: The neuron is “at rest,” with more negative charge inside than outside.
Stimulus: Something triggers the cell (like a chemical signal).
Depolarization: Sodium (Na⁺) channels open, and Na⁺ rushes in, making the inside more positive.
Repolarization: Potassium (K⁺) channels open, and K⁺ flows out, bringing the cell back to negative.
Return to Rest: The cell resets to be ready for the next signal.
10
Q
Electrical Info
A
Movement of Ions (Na+,K+) using Voltage-gated channel (proteins)
11
Q
What is a voltage-gated channel?
A
A protein in a cell’s membrane that opens or closes depending on the electrical charge (voltage) across the membrane.
12
Q
1) Action Potential Arrives at Axon Terminal
A
An electrical signal (action potential) travels down the axon to the axon terminal of the presynaptic neuron (transmitting info before synapse)
13
Q
2) Voltage-Gated Ca²⁺ Channels Open
A
The change in voltage causes voltage-gated calcium (Ca²⁺) channels to open
14
Q
3) Ca²⁺ Enters the Axon Terminal
A
Calcium ions enter the cell, triggered by the electrical signal.
This step links the electrical signal to the chemical process, triggering neurotransmitter release.
15
Q
4) Synaptic Vesicles Release Neurotransmitters (Chemical transmission)
A
The influx of Ca²⁺ causes synaptic vesicles (which carry neurotransmitters) to fuse w/ the pre-sypnatic membrane & release neurotransmitters into the synaptic cleft. This is the chemical transmission step
16
Q
5)Neurotransmitters Bind to Receptors on Postsynaptic Cell
A
Neurotransmitters diffuse across the synapse and bind to ligand-gated ion channels on the postsynaptic neuron’s dendrite
17
Q
6) Ions Flow In – Signal Converted Back to Electrical
A
When neurotransmitters bind, the ligand-gated channels open, allowing ions (e.g., Na⁺) to enter the postsynaptic neuron.
This causes depolarization (a rise in voltage), potentially triggering a new action potential if the threshold is reached.
18
Q
Ligand-Gated Ion Channels
A
Postsynaptic receptors)
Open when neurotransmitters bind to them (CHEMICAL)
19
Q
4) Hyperpolarization
A
Too much K⁺ leaves, causing the inside to dip below resting potential
Eventually, K⁺ channels close and the Na⁺/K⁺ pump restores resting potential
20
Q
Neurotransmitters
A
Chemical messengers (e.g., dopamine, serotonin, acetylcholine) that carry the signal across the synapse.
21
Q
Receptor Proteins
A
Located on the postsynaptic neuron; bind neurotransmitters & control ion flow
22
Q
Mechanically-gated channels:
A
Open/ close in response to physical forces—like stretching, pressure, or vibration—rather than changes in voltage or chemicals.
23
Q
How does information get to the brain?
A
Chemosensation: Chemical sensing,
sound/hearing,
visual systems
Environmental Stimulus → Sensory Receptor → Transduction → Afferent Neuron → CNS → Brain Perception
24
Q
Sensory Receptor Activation
A
Sensory receptors convert the physical or chemical stimulus into a graded potential—a small change in membrane voltage, If the graded potential is strong enough, it triggers an action potential
25
Stimulus Detection
(Environmental Input) A stimulus from the environment (light, sound, pressure, temperature, chemicals, etc.) interacts with specialized sensory receptors.
26
Transduction (Converting Stimulus to Electrical Signal)
converting a stimulus into an electrical signal. In many cases, ion channels open due to the stimulus (directly or via second messengers), causing depolarization.
If depolarization reaches the threshold, an action potential is generated in the sensory neuron
27
Transmission Along Afferent Neurons
The action potential travels along the afferent (sensory) neuron toward the central nervous system (CNS). The neuron’s axon conducts the signal to the spinal cord or brainstem, depending on the location and type of receptor.
28
Gustation
taste
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Stimulus (gustation)
A tastant (e.g., sugar, salt, acid) is a chemical compound
30
What is the receptor proteins of tastants? ion channels & ___ channels
Ion channels & ligand-gated channels
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Epithelial sensory cell for gustation
Taste receptor cell
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Vesicles with neurotransmitters for gustation
Serotonin or ATP
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Neurotransmitter Receptor for Gustation: ___ channel
Ligand-gated channels
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Dendrite of Afferent Neuron for gustation
Primary gustatory neuron "afferent neuron"
35
Sweet, Bitter, and Umami all bind to and activate what type of channels?
Ligand-gated
36
Salty and sour is caused by what and what channels?
Salty: Na+ flow thru ion channels
Sour: H+ flow thru ion channels & cause depolarization (taste receptor cell)
37
Transduction
The process by which a stimulus (e.g., a hormone, a neurotransmitter, or sensory information) outside a cell is converted to an intracellular signal required for a cellular response. Usually involves a specific sequence of molecular events called a signal transduction pathway, which may amplify the signal.
38
Transmission
process by which sensory receptors detect stimuli (such as light, sound, touch, or temperature) and convert them into electrical signals
39
Saltiness
due to sodium ions (Na+) dissolved in food. These ions flow into certain taste cells through open Na+ channels and depolarize the cells’ membranes.
40
Sourness
presence of protons (H+), which flow directly into certain taste cells through H+ ion channels and depolarize the membrane.
41
Bitterness
the binding of the bitter molecule to a membrane-bound receptor that initiates a signaling pathway inside the cell. (activates ligand-gated channels) Ligand binds → second messenger → ion channel activity changes
42
Sweetness
Sugars bind to a receptor on surface of cell & activate ligand-gated channels, receptor specific for different sugars (fructose, sucrose, glucose)
a single receptor protein has binding sites for multiple types of sweet compounds, meaning that a variety of molecules can stimulate each sweet receptor cell.
43
Umami
Glutamate triggers the sensation called umami, which is the meaty taste of (MSG). Glutamate is sensed by one particular pair of the three receptor proteins
detected by glutamate
44
Taste transduction
population coding: 1 tastant activates many different neurons
45
A taste receptor cell is shown to generate receptor potentials in response to sour stimuli (such as citric acid) and sweet stimuli (such as fructose). Which type(s) of receptors must be present in the membrane of this receptor cell?
Both specialized ion channels and membrane-bound receptor proteins.
46
In the presence of a bitter tastant, the taste receptor cell is depolarized by:
the binding of the bitter molecule to a membrane-bound receptor that initiates a signaling pathway inside the cell.
47
Afferent division
transmits info abt the internal & external environ to CNS. Consists mainly of sensory neurons.
48
Efferent division
carries commands from CNS
to rest of body. Consists primarily of motor neurons.
49
Mechanosensation
physical movement, pressure wave = sound wave,
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frequency
affects pitch (how many humps in between one cycle)
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Amplitude
how tall humps are = volume (taller = louder)
52
Sound Waves
info (fluid) cochlea allows for conversion of sound waves to another form of info
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Outer Ear
Pinna (Auricle): Captures sound waves from the environ
Auditory Canal: Channels sound waves toward the eardrum
54
Middle Ear
Tympanic Membrane (Eardrum): Vibrates in response to sound waves.
bones amplify vibrations & transfer them to the inner ear
55
Inner Ear
Cochlea: A spiral-shaped, fluid-filled structure where mechanical vibrations are transformed into electrical signals.
56
Inside the cochlea
Basilar membrane: Moves in response to vibrations.
Hair cells (sensory receptors): Sit on the basilar membrane and have Stereocilia that bend with movement.
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What does the Stereocilia bending open in cochlea?
Bending opens mechanically gated ion channels, leading to depolarization & neurotransmitter release.
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Auditory Nerve (Cochlear Nerve)
Hair cells release neurotransmitters that activate afferent neurons in the auditory nerve.
These neurons carry action potentials to the brainstem.
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Auditory Cortex (in Temporal Lobe)
sound is consciously perceived & interpreted (e.g., speech, music, pitch, volume).
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Brainstem Nuclei
Cochlear nuclei (in the medulla): First synapse in the brain
Signals are processed and then passed through other brainstem structures
thalamus relays auditory information to the cortex.
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Sound Transduction
single line directed -> sound
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Stimulus (gustation/auditory)
A sound wave in hearing) reaches a specialized receptor cell. (a hair cell in the cochlea)
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What are the receptor proteins of auditory system?
Mechanically-gated channels
64
What is the epithelial sensory cell of the auditory system?
Stereocilia
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What is the vesicle w/ neurotransmitter called in the auditory system?
Glutamate
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What type of channels are activated by neurotransmitters on the sensory neuron auditory?
Ligand-gated channels.
67
Where do neurotransmitters bind on the afferent neuron (auditory)?
dendrite of the afferent neuron: spiral ganglion.
68
What happens if enough neurotransmitter binds to the afferent neuron?
It fires an action potential that travels to CNS
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How do hair cells respond to sound stimuli?
Each hair cell responds to a single sound stimulus.
70
How is sound information carried to the brain?
By a labeled line of afferent neurons
71
How is taste information encoded?
By population coding
72
Can taste receptor cells respond to more than one tastant?
Yes, they can respond to multiple tastants.
73
How is taste information brought to the brain?
Through populations of afferent neurons, each carrying mixed signals.
74
Where on the basilar membrane in the cochlea do high-frequency sounds (e.g., 16,000 Hz) cause the most depolarization?
Near the base of the basilar membrane.
75
What are the properties of the base of the basilar membrane?
It is stiff, thick, and narrow—sensitive to high-frequency vibrations
76
What are the properties of the apex of the basilar membrane?
It is flexible, wide, and responds to low-frequency sounds.
77
What type of channel does the auditory system use to detect vibrations?
Mechanically-gated channels.
78
no
79
What type of channels does the gustatory system use to detect tastants?
Ligand-gated channels
80
No
81
What do both the auditory and gustatory systems end with?
Neurotransmitter release that activates a sensory neuron
82
Q: What’s the key difference between auditory and gustatory signal detection?
Auditory uses mechanical signals; gustatory uses chemical (ligand) signals.
83
What is membrane potential/voltage?
A difference in electric charge across a cell membrane; a form of potential energy.
84
What is a synapse?
interface between two neurons, or between a neuron and an effector cell.
85
What is the synaptic cleft?
space between two communicating cells at a synapse, across which neurotransmitters diffuse.
86
What are synaptic vesicles?
Small vesicles that contain neurotransmitters and release them into the synaptic cleft by exocytosis.
87
What is a presynaptic neuron?
carries an electrical signal (an action potential) down its axon,A neuron that transmits signals, usually by releasing neurotransmitters.
88
What is a postsynaptic cell?
A cell that receives signals from a presynaptic neuron, typically via neurotransmitters.
89
What is a neurotransmitter?
A molecule that transmits signals between neurons or from a neuron to a muscle or gland cell.
90
What is a ligand-gated channel?
An ion channel that opens when a specific molecule (ligand) binds to it.
91
What is evolution?
A change in the genetic information and characteristics of a population over time.
92
What does "genetic characteristics" refer to in evolution?.
Traits resulting from DNA—the chemical that carries genetic info.
93
What is a population in evolutionary terms?
A group of individuals of the same species.
94
What does “over time” mean in evolution?
Changes across multiple generations, often over millions of years.
95
What is the core idea of the theory of evolution?
All organisms are related by common ancestry & change over time thru natural selection & other processes.
96
What is another way to define evolution?
A change in allele frequencies in a population over time.
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What is macroevolution?
Large-scale differences among species, formation of new species (info)
98
What is microevolution?
Small changes w/ in a single population over time.
99
Is evolution the same as an individual adapting to the environment?
NO
100
Does evolution drive organisms toward “higher” life forms?
NO
101
Does evolution cause individuals to act for the good of the species?
NO
102
What is Darwin’s phrase for the pattern of evolution?
Descent with modification
103
What does “descent with modification” mean?
Species today are descendants of past species that have changed over time.
104
What is the difference between extinct and extant species?
Extinct species are no longer living; extant species are currently living
105
What are two key ideas in evolution based on fossil evidence?
1) Species change over time; 2) Species are related by a common ancestor.
106
What are the 4 pieces of evidence for species change through time?
1) Earth is very old
2) Extinctions
3) Changes in form: transition species, law of succession
4) Vestigial traits
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What does Earth's age tell us about species change?
There has been enough time for species to change and evolve.
108
What evidence supports that Earth is very old and species have changed?
Fossil records.
109
How are traits from extinct species seen today?
Traits have been modified and are present in modern species.
110
What is true about most species that have ever lived?
Most are extinct.
111
What is the Law of Succession?
Fossils and modern species from the same geographic region show similarities.
112
What are transitional species (or transitional fossils)?
Fossils that show intermediate traits between ancestral and modern species.
113
What is an intermediate trait?
A trait that is between the condition of an ancestral species and a derived (younger) species.
114
What are vestigial traits?
Reduced / useless structures that were functional in ancestors but may have no or reduced function in current species.
115
What are the 3 pieces of evidence for Species related by common ancestry?
1) Similar species near each other geographically
2) Homology (Structural, genetic, developmental)
3) Observable (w/in the human lifespan) changes in species over time
116
What does it suggest when similar species are found near each other geographically?
That they likely evolved from a common ancestor & adapted to different environments.
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What is homology?
A similarity among organisms of different species due to shared ancestry.
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What does it mean if features are homologous?
they have a common origin, but have evolved modifications for different functions.
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What is genetic homology?
Similarity in DNA, RNA, or protein sequences due to inheritance from a common ancestor.
120
What is developmental homology?
A similarity in embryonic form or early development due to shared ancestry.
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What is structural homology?
may have diff functions but similar structures in species body parts
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What is an example of evolutionary change that has been directly observed?
One species splitting into two or more descendant species (speciation).
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What does "heritable" mean?
A trait that can be passed from one generation to the next.
124
What is speciation?
The evolution of two or more distinct species from a single ancestral species.
125
What did Darwin’s finches demonstrate during a drought?
Natural selection—they evolved larger beaks to survive.
126
What does the evolution of antibiotic-resistant bacteria like MRSA demonstrate?
Artificial selection due to human use of antibiotics
127
What does the fossil record show?
A historical record of life & evidence of species changing over time.
128
What is comparative embryology?
Similarities in early development across species that point to shared ancestry.
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What does molecular biology (DNA) reveal about species?
Genetic similarities confirm evolutionary relationships
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What is biogeography?
The study of how geographic isolation leads to species divergence.
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What is direct observation in evolution?
Watching evolutionary changes happen in real-time, like antibiotic resistance.
132
What is convergent evolution?
Unrelated species develop similar traits due to similar environments, not shared ancestry.
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What are Darwin’s Four Postulates of Natural Selection?
1) Variation exists
2) Variations must be HERITABLE
3) More offspring produced than survive
4) offspring w/ certain heritable traits are more likely to survive & reproduce
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Why is variation important in a population?
Without variation in traits, there’s nothing for natural selection to act on.
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What is inheritance in the context of natural selection?
Traits must be heritable—passed from parent to offspring—for natural selection to affect future generations.
136
What happens if traits aren’t heritable?
Any advantages will not be passed on to the next generation.
137
What is overproduction in evolution?
More offspring are produced than can survive, leading to competition.
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Why does overproduction matter for natural selection?
Only some individuals survive and reproduce, increasing selective pressure.
139
What is differential survival and reproduction?
Individuals with certain heritable traits are more likely to survive and reproduce.
140
What happens to favorable traits over time?
They become more common in the population due to natural selection
141
What is fitness in biology?
The ability to reproduce viable offspring relative to others in the same species.
142
What is an adaptation?
A heritable trait that increases fitness in a specific environment.
143
What do adaptations do?
Help individuals survive and reproduce better than those without the trait.
144
What is the process of evolution driven by?
Natural selection—where nature selects for traits aiding survival and reproduction.
145
How does natural selection work?
Traits that improve fitness become more common over time due to unequal survival.
146
What is directional selection?
A mode of natural selection that favors one extreme phenotype, shifting the population’s average in one direction & decreasing genetic variation.
147
What is artificial selection?
Selective breeding by humans to enhance desirable traits, sometimes leading to speciation.
148
What is stabilizing selection?
Natural selection that favors the middle of the phenotypic range, eliminates extremes, and reduces genetic variation.
149
What is disruptive selection?
Natural selection that favors extreme phenotypes at both ends, increases or maintains genetic variation, and may sometimes lead to new species.
150
What does a fitness function show?
It shows the % survival of traits or groups ("bins") based on their fitness.
151
What is balancing selection?
Selection where no single phenotype is favored; maintains an overall balance of alleles and preserves genetic variation.
152
How does fitness relate to natural selection?
Fitness increases when traits are adaptive to selective pressures under different modes of natural selection.
153
What are the four processes of evolution?
1) Mutations
2) Gene Flow
3) Genetic Drift: Founder effect, Bottleneck effect
4) Natural Selection
154
How does natural selection affect genetic diversity?
It lowers genetic diversity because only individuals with the best adaptive traits survive and reproduce.
155
What is a mutation?
A random, spontaneous change in DNA that creates new alleles, increasing genetic variation. It can decrease, increase, or not affect fitness.
156
How is diversity affected by mutations
Increase genetic diversity
157
How is fitness affected by mutations?
Possible to increase, decrease, or not affect fitness but decreasing most likely
158
Are mutations adaptive?
NO
159
What is a somatic mutation?
A mutation that occurs in body cells, any cell that is not a gamete
160
Are somatic mutations heritable?
No
161
What are germ-line mutations?
Occurs in gametes, only sperm cells
162
Are germ-line mutations heritable?
Yes
163
Which mutations (somatic or germ-line) are necessary for evolution and why?
Germ-line bc they are inherited b y offspring, they contribute & are necessary to evolution
164
What is lateral gene transfer?
The transfer of DNA between two different species, increasing genetic variation.
165
What is a beneficial allele?
An allele that increases an individual’s fitness.
166
What is a neutral allele?
An allele that has no effect on fitness.
167
What is gene flow?
The movement of alleles between populations
168
How is diversity affected by gene flow?
Increases genetic diversity
169
How is fitness affected by gene flow?
Possible to increase/decrease but decreasing most likely
170
What is genetic drift?
A random change in allele frequencies, more impactful in small populations.
171
What is the founder effect?
migration of a small subgroup of a population to form a new population, causes change in allele frequencies
172
How is genetic diversity affected by the founder effect?
Decreases diversity
173
How is fitness affected by founder effect?
possible to increase, decrease, but decreasing most likely
174
What is a genetic bottleneck?
A large random death event that drastically reduces population size and diversity without selection.
175
How is diversity affected by genetic bottleneck?
Decrease diversity
176
How is fitness affected by a genetic bottleneck?
possible to increase/decrease but decreasing most likely
177
What is the overall effect of natural selection on a population?
It maintains, increases, or reduces genetic variation but always increases fitness over time.
178
What is a species?
An evolutionarily independent population or group of populations, generally distinct in appearance, behavior, habitat, or genetics.
179
What is speciation?
The evolution of two or more distinct species from a single ancestral species.
180
What is the morphospecies concept?
Species are defined by morphological (physical) traits/ phenotypes and similarities.
181
What is a cryptic species?
Different species that look very similar but are genetically distinct.
182
What is a polymorphic species?
A species with two or more distinct phenotypes in the same interbreeding population.
183
What is the biological species concept?
A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions.
184
What is prezygotic isolation?
Barriers before fertilization that prevent mating between species.
185
What are the prezygotic barriers that cause reproductive isolation?
Geographic, habitat/ecological, temporal, behavioral, gametic, mechanical
186
What is postzygotic isolation?
Barriers after mating, like hybrid death or reduced hybrid fitness.
187
What are the postzygotic barriers that cause reproductive isolation?
Reduced hybrid viability & hybrid sterility
188
What is a synapomorphy?
A shared, derived trait present in a group's most recent common ancestor.
189
What is the phylogenetic species concept?
A species is the smallest group of individuals that share a common ancestor and form one branch on the tree of life (a monophyletic group).
190
What is a monophyletic group?
An ancestor and all of its descendants, but no others.
191
What is a subspecies?
A population with distinct traits and some genetic differences but not enough to be a separate species.
192
What are the applications of the Morphospecies Concept?
Fossils identification, Extinct organisms, When genetic data is unavailable
193
What are the limitations of the Morphospecies Concept?
Different species may look similar (cryptic species), making identification difficult.
194
What are the applications of the Biological Species Concept?
Most animals, Many plants
195
What are the limitations of the Biological Species Concept?
Doesn’t work for asexual organisms or fossils.
196
What are the limitations of the Phylogenetic Species Concept?
Requires detailed genetic analysis and clear phylogenies.
197
What are the applications of the Phylogenetic Species Concept?
All organisms (including asexual & extinct species)
198
What is vicariance in allopatric speciation?
A physical barrier splits one population into two isolated groups, leading to divergence and speciation.
199
What is allopatric speciation?
Speciation due to geographic isolation; populations are separated by physical barriers like mountains, rivers, or habitat loss.
200
What is dispersal in allopatric speciation?
A few individuals move to a new area (e.g., across a barrier like water to an island) and become isolated from the original population.
201
What causes genetic divergence in allopatric speciation?
Mutation, natural selection, and genetic drift over time in isolated populations.
202
What is sympatric speciation?
(same area) Speciation that occurs without geographic separation; populations become genetically isolated while living in the same area.
203
What are causes of sympatric speciation?
Behavioral differences (e.g., mating calls)
Temporal isolation
Mechanical isolation
Ecological isolation
204
Temporal isolation
(breeding at different times)
205
Mechanical isolation
(incompatible reproductive anatomy)
206
Ecological/habitat isolation
different habitats or niches within the same area)
207
Behavioral Isolation
different species don't mate because of differences in behavior — especially behaviors related to courtship and mating
208
Gametic Isolation
fertilization can't happen even if gametes (egg and sperm) meet, because they are incompatible
209
Reduced hybrid viability
hybrid offspring either die early in development or survive poorly.
210
hybrid sterility
hybrid offspring are healthy but cannot reproduce
211
How does dispersal differ from vicariance?
Dispersal: Few individuals move across a barrier to a new area
Vicariance: A barrier forms, splitting one population into two
212
What is a phylogeny?
The evolutionary history of a group of organisms.
213
What is a phylogenetic tree?
A branching diagram that shows evolutionary relationships among species or taxa.
214
What is a taxon (taxa)?
Any group of organisms at any classification level (e.g., species, genus, family).
215
Any group of organisms at any classification level (e.g., species, genus, family).
A sequence of species that descend from a common ancestor.
216
What does a branch on a phylogenetic tree represent?
A population or lineage evolving over time.
217
What is a node on a phylogenetic tree?
A branching point representing the most recent common ancestor of descendant groups.
218
What is a trait?
A heritable characteristic like fur, wings, or DNA sequences.
219
What is a synapomorphy?
A shared, derived trait from a recent common ancestor, used to identify clades.
📌 Example: Fur in mammals.
220
What is a common ancestor?
An ancestral species shared by two or more taxa, shown as a node on the tree.
221
What is a clade (monophyletic group)?
A group with a common ancestor and all of its descendants..
222
What is a paraphyletic group?
A group that includes a common ancestor but not all its descendants.
❌ Example: Reptiles excluding birds.
223
What is a polyphyletic group?
A group that lacks the most recent common ancestor; based on convergent traits.
❌ Example: Bats and birds grouped for flight.
