Final review Flashcards
ways in which natural selection
can affect or shape a population:
- Stabilizing selection
- Directional selection
- Diversifying selection
- Frequency-dependent selection
- Sexual selection
Species concepts
-Morphological species concept: Morphological characteristics
-Biological species concept: Whether they are likely to mate and have fertile offspring.
-Ecological species concept: The ecological niche or geographical area that individuals occupy
-Genetic species concept: Genetic differences
Allopatric speciation
Speciation due to geographical barriers such as mountains, rivers, roads.
Sympatric speciation
Reproductive isolation may occur due to genetic changes, e.g. mutations, if the mutations causes a change in mating behaviour or a change in pollinators.
Genetic diversity
Genotype diversity/variation among individuals within the same population and species.
Ecosystem diversity
The number, size and variation of different ecosystems and habitats within an area or region.
Species diversity
Species richness: The number of species in an area.
Species evenness: The relative abundance of a species in an area.
Alpha diversity =
the number of species in a local
area.
Gamma diversity =
The total number of species in
a larger area/region.
Beta diversity =
Gamma/alpha. The change
in species from one area to
another (a measure of
heterogeneity).
Measuring ecosystem health and integrity
-Ecosystem services (e.g. erosion
control, water regulation, pollination)
-Natural processes (e.g. nutrient cycling)
-Natural disturbances (e.g. fire, grazing)
-Functional and structural diversity
Indicator species (diversity and abundance)
Latitudinal Diversity Gradient
Biodiversity tend to be high near the equator and low close to the
poles.
What type of evidence would support the
immigration/destination hypothesis?
A. Many species originate in the tropics and stay there.
B. Many species originate in the tropics, but then spread elsewhere.
C. Many species originate near the poles, but then spread to the tropics.
D.Many species originate near the poles and stay there.
Many species originate in the tropics, but then spread elsewhere.
Productivity
is the rate of growth and production of biomass in an ecosystem.
Primary productivity
plant growth = rate of photosynthesis
Secondary productivity
animal (and other heterotrophs, i.e.
consumers) growth.
4 hypotheses of tropics biodiversity
Hypothesis #1: Immigration/destination (warm and wet climate = high productivity)
Hypothesis #2: The cradle hypothesis (It explains how and why species have accumulated in the tropics through natural selection and speciation)
Hypothesis #3: The museum hypothesis
(Speciation has taken place over a longer time in the tropics which may explain why it has more species than the tundra.)
Hypothesis #4: The productivity hypothesis
(An area with high productivity is likely to have a high variety of resources and many niches. It can support many different species with less competition)
Regional species pool e.g. Central SK (filters)
- Dispersal filter
Some of these species will disperse to a
certain area. - Environmental (abiotic) filter
Some of the species that disperse there will be able to germinate and grow there. - Species interaction (biotic) filter
Some of those species will be able to survive interaction with the other species present there.
Competitive Exclusion Principle
If the niches of two species are too similar, i.e. if they overlap too much, they are not likely to coexist.
What will happen if sea stars are removed from the intertidal zone community?
A. Species richness will increase as the species it preys on
will survive longer.
B. Species richness will increase as there will be more resources for other species.
C. Species richness will stay the same as other species will take its role.
D. Species richness will decrease as one of the prey species will outcompete the others.
D. Species richness will decrease as one of the prey species will outcompete the others
Factors that may have caused historic mass extinctions:
Volcano eruptions due to tectonic plates moving and consequent changes in the climate (warming and cooling).
* Ocean acidification.
* Asteroid impacts.
* Plants increased the oxygen and decreased carbon dioxide in
the atmosphere => cooling of the climate.
* Increased weathering of rocks and the release of phosphor due
to an increase of land plants led to an increase in algae and
ocean anoxia (oxygen poor dead zones).
Explain how historic thoughts on evolution have contributed to modern theories.
-Plato and Aristotle (384-
322 BC) “Species are fixed and
unrelated.”, “Animals are arranged
from low to high complexity.”
-Carolus Linnaeus (1707-1778)
“Species should be named and organized based on their similarities”.
-Georges Cuvier (1769-1832). “Earth goes through sudden changes or catastrophes that lead to the extinction of many species.”
-Jean Baptiste Lamarck
(1744-1829)
“Organisms will change if
they need to do so.” giraffe analogy
-Charles Darwin (1809-1882) and Alfred Russel Wallace (1823-1913)
“All species on Earth have a common ancestor.”
Compare and contrast deductive and inductive reasoning.
-Compare and contrast deductive and inductive reasoning.
-Scientists use deductive reasoning when they make specific predictions based on general theories and information.
Explain the difference between microevolution and macroevolution.
Micro- Small-scale evolutionary changes within a population or species over a short period of time.
Macro- Large-scale evolutionary changes that occur over long time periods and can lead to the emergence of new species or groups of organisms.
Differentiate among intrasexual and intersexual selection and explain when we can predict each selection to be most common.
Intrasexual selection
Males defend their territory or food patch and fight off other males that try to mate with females in that area. Common in areas where food sources are “patchy”.
Intersexual selection
Males attract females. Females are choosy and choose males with the most showy and costly features. Common in areas where food sources are dispersed more evenly.
Explain how the bottleneck and founder effects relate to genetic drift and why each of these effects may lead to evolution.
Both the bottleneck effect and the founder effect are specific types of genetic drift
bottleneck effect
Happens when a large population is drastically reduced by a random event (e.g., natural disaster, disease, hunting).
Founder effect
Occurs when a small group breaks off from a larger population and establishes a new population in a different location.
Explain why small populations are at higher risk of genetic drift.
-random events have a bigger impact
-Imagine flipping a coin:
Flip it 10 times (like a small population): You might get 7 heads and 3 tails. That’s a big swing.
Flip it 1,000 times (like a large population): You’ll likely get close to 500 heads and 500 tails. The chance evens out.
Give examples of analogous structures.
Wings of Birds 🐦 and Bats 🦇 vs. Insects 🐝
Give examples of homologous structures
Forelimbs of Vertebrates
what is the difference between analogous structures vs homologous structures
Homologous: Structures that come from a common ancestor, even if they now have different functions.
Analogous: Structures that perform a similar function, but do not share a common ancestor.
what does polyploidy mean?
Having more than two complete sets of chromosomes in a cell.
Compare and contrast autopolyploidy and allopolyploidy.
Autopolyploidy = one species copies its own chromosomes (when polyploidy makes a copy of itself)
Allopolyploidy = hybrid of two species + chromosome doubling
Describe what a hybrid zone is and explain when each hybrid zone type is likely to occur.
-A hybrid zone is a geographic area where two distinct species or genetically different populations meet, interbreed, and produce hybrid offspring.
-Reinforcement: Likely when hybrid offspring are viable but have reduced fitness, and when there is ongoing contact and interbreeding between the parent species.
-Fusion: Likely when species are only slightly diverged and hybrid offspring are viable and fertile.
- Stability: Likely when hybrid offspring are viable but have reduced fitness, and when there is ongoing contact and interbreeding between the parent species.
Explain what resource partitioning is and how it allows species to coexist.
Resource partitioning is a process where similar species divide up resources in an environment to reduce direct competition and allow them to coexist.
Explain the difference between a species’ fundamental and realized niche
fundamental niche: The full range of environmental conditions and resources a species could use or survive in, without competition or interference from other species.
realized niche: The actual range of conditions and resources the species does use in nature, after interactions like competition, predation, or disease are taken into account.
In Short:
Fundamental niche = what’s possible
Realized niche = what’s actually used
Predict what happens when two species compete for the same niche using the competitive exclusion principle.
One species will outcompete the other, leading to the exclusion (local extinction) of the less competitive species.
Differentiate between habitat loss, degradation and fragmentation.
Habitat loss- The complete destruction of a natural habitat, making it no longer able to support the species that lived there.
Habitat degradation- The decline in habitat quality, making it less able to support species.
Habitat fragmentation- When a large, continuous habitat is broken into smaller, isolated patches.
Compare and contrast an ecosystem and an ecological community, highlighting their key components and interactions.
Ecological community-All the living organisms (biotic factors) in a particular area that interact with one another.
Ecosystem- All the living organisms (biotic) and the nonliving environment (abiotic) they interact with in a specific area.
Describe predator-mediated coexistence and explain how predators influence species diversity.
Predator-mediated coexistence occurs when the presence of a predator allows multiple prey species to coexist by controlling the population of the dominant competitor.
Define a keystone species and explain how it contributes to maintaining biodiversity.
It helps regulate populations of other species.
It can control dominant species, preventing them from outcompeting others.
It can create or maintain habitats that other species rely on.
Its removal can lead to ecosystem collapse or a sharp drop in biodiversity.
Provide an example of a trophic cascade and explain how it may affect species richness in a community.
Top Predator Removed: Wolves gone.
Herbivore Population Increases: Elk grow in number and over-browse vegetation.
Vegetation Declines: Young trees, shrubs, and grasses decrease.
Habitat Loss: Fewer plants mean fewer habitats and food sources for: Birds,
Beavers, Insects
Fish (indirectly, via loss of shading and erosion control)
Species Richness Drops: Less plant cover and fewer niches = fewer species overall.
Explain what an edge effect is and how it may affect biodiversity. (abiotic and biotic)
Abiotic effects:
* More light
* Dryer soil
* Higher wind speed
* Higher temperature
Biotic effects:
* Altered plant community due to chance in abiotic factors.
* Altered dispersal of plants
* Increase in invasive plants (facilitated dispersal and altered abiotic
conditions).
* Increase in competition.
* Increase in predation (e.g. less shelter and camouflage and changes
in predator behaviour)
Explain reasons why overharvesting and overexploitation takes place.
-economic demands
-Growing populations
-New technology
Explain several benefits of biodiversity and provide several reasons why we should care about losing species.
-Pollination (e.g., bees helping grow crops)
-Many modern medicines come from natural sources (e.g., aspirin from willow bark)
-Industries like fishing, forestry, agriculture, and ecotourism depend directly on biodiversity.
Why should we care?
-Species are interconnected—losing one can trigger a domino effect, disrupting entire ecosystems.
-Fewer species means reduced resilience—ecosystems may no longer provide clean water, fertile soil, or climate stability.
Distinguish between keystone species, foundation species and endemic species and explain the significance of each of them.
keystone- A species that has a disproportionately large effect on its ecosystem relative to its abundance
Foundation- A species that is abundant and forms the physical basis or structure of a habitat. (like trees)
Endemic-A species that is found in one geographic location only—nowhere else in the world.
Distinguish between provisioning, regulating, supporting and cultural ecosystem services and give examples of each.
Provisioning: These are the products we get directly from ecosystems. (foods like fish)
Regulating: These are the natural processes that regulate the environment. (pollination)
Supporting: These are the underlying natural processes that make all other services possible. (soil formation or nutrient recycling).
Cultural: These are the non-material benefits we get from ecosystems. (like hiking)
What is stabilizing selection?
Favored Traits: Intermediate traits (more common traits due to alleles)
Example: Human birth weight — very low and very high weights have higher mortality rates, so average birth weights are selected for.
Effect on Population: Reduces variation; maintains status quo.
What is Directional Selection
Favored Traits: One extreme of a trait
Example: In a population of birds, if longer beaks help access food better, birds with longer beaks will be more likely to survive and reproduce.
Effect on Population: Shifts the average trait in one direction over time.
What is Disruptive Selection
Favored Traits: Both extremes of a trait
Example: In an environment with black and white rocks, black and white rabbits might blend in better than gray ones, making gray (intermediate) rabbits more vulnerable to predators.
Effect on Population: Can lead to increased variation and potentially to speciation (formation of new species).
examples of prezygotic barriers
-habitat isolation
-temporal isolation
-behavioral isolation
examples of postzygotic barriers
-hybrids result in sterility
-hybrids development or survival is impaired
what is sexual selection?
occurs when individuals within a species compete for mates or are chosen by mates based on certain traits. (intrasexual selection and intersexual selection)
Which of the following statements is FALSE?
Punctuated equilibrium is most likely to occur in a small population that experiences a rapid change in its environment.
Gradual speciation is most likely to occur in species that live in a stable climate.
Punctuated equilibrium is most likely to occur in a large population that lives in a stable climate.
Gradual speciation and punctuated equilibrium both result in the divergence of species.
Punctuated equilibrium is most likely to occur in a large population that lives in a stable climate.
is false
what are biodiversity hotspots
Regions with high numbers of endemic species.
Why is species richness not always a good indicator of ecological health?
High species richness can include invasive species.
Which processes do you think determine the number of species on a landscape/ecosystem scale, e.g., an island?
Immigration and emigration
Speciation only
Speciation and extinction
Immigration and extinction
Immigration and emigration
What species concept emphasizes reproductive isolation?
Morphological
Biological
Ecological
Genetic
Biological
Natural selection is an example of ______.
A bit of both microevolution and macroevolution
Neither microevolution nor macroevolution.
Macroevolution only
Microevolution only
Microevolution only
How does genetic evidence support evolution?
It reveals shared genetic sequences among species.
Gene flow can counteract genetic drift by:
Introducing new alleles into a population.
Which process contributes the most to genetic variation in sexually reproducing populations?
Genetic recombination
According to the RNA world hypothesis, what role did ribozymes play in early life?
They formed membranes around protocells.
They were responsible for photosynthesis.
They were the first DNA molecules.
They catalyzed their own replication and protein production.
They catalyzed their own replication and protein production.
