BIS 2B - Final Exam

Biological Species Concept

Biological Species Concept

A species is a group of actually or potentially interbreeding individuals that is reproductively isolated from other groups.

-Pros: straightforward and easy to understand, based in HWE mechanisms

-Cons: requires knowledge of mating systems, does not apply to asexual species, some mating systems are more complex than this definition allows (example: Ensatina salamander ring species).

-Does NOT work for: extinct organisms, asexual species, populations with continuum of interbreeding (ring species)

Morphological Species Concept

A species is a group of organisms that have similar physical traits (morphology).

-Pros: good for groups where other data are limited.

-Cons: morphological similarity can be misleading.

-Does not work well for species that experience convergent evolution (will overestimate relatedness). Generally less accurate/reliable than other species concepts

Phylogenetic Species Concept

A species is a group of organisms that shares a common ancestor and can be distinguished from other organisms by particular traits (especially genetic similarity).

-Pros: based in evolutionary history, applies to all organisms (all organisms have DNA).

-Cons: requires modern genetic and computational tools.

-Does NOT work for extinct species (can sometimes get DNA from recently extinct groups)

Polyploidy

(How does it influence reproductive isolation and speciation?)

Polyploidy means having more than two sets of chromosomes.

Polyploids are reproductively isolated from diploids because their offspring will have odd numbers of chromosome sets, which cannot easily be divided during meiosis and so they will be sterile (postzygotic barrier: reduced hybrid fertility). Polyploids can successfully breed with other polyploids with the same number of chromosomes, which means we consider them separate species from their diploid relatives.

For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern

(Allopatry through vicariance)

Some sort of physical geographic barrier separates the population into roughly equal halves. Over time, differences in mutations, genetic drift, selection, etc result in genetic differences between the disconnected halves. Eventually, these differences are significant enough to produce reproductive barriers between the two groups (will not successfully interbreed if they come into contact again), so we then consider them separate species.

For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern

(Allopatry through the founder effect)

A small subset of the population colonizes a new area (geographically separate from the larger 'background' population). Over time, differences in mutations, genetic drift, selection, etc result in genetic differences between the two groups. Eventually, these differences are significant enough to produce reproductive barriers between the two groups (will not successfully interbreed if they come into contact again), so we then consider them separate species.

For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern

(Parapatry)

One 'edge' of the population experiences different conditions than the broader population; the groups are not geographically distinct, but are also not fully intermixed, they are adjacent to one another or partially overlapping. Over time, differences in mutations, genetic drift, selection, etc result in genetic differences between the two portions of the population. Eventually, these differences are significant enough to produce reproductive barriers between the two groups (will not successfully interbreed if they come into contact again), so we then consider them separate species.

For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern

(Sympatry)

Some genetic change (often a mutation or behavioral shift) arises in one or a few individuals that are distributed across a population. This mutation or behavioral change results in a reproductive barrier between these individuals and the rest of the population. As the mutation or behavioral change becomes more common, we see two distinct groups emerge, which we consider separate species.

*An important difference between sympatry and parapatry is that the two groups are fully intermixed in sympatry (while they are adjacent or tangential to one another in parapatry).

Why does specialization lead to faster speciation rates than groups that are generalists?

Specialization often produces behavioral or geographic isolation.

EX: Specializing on a particular pollinator means that pollinator will likely not carry pollen from one species to another (behavioral isolation). Specialization on a particular plant diet means the insects will likely only mate with other individuals on that type of plant (ecological habitat isolation).

Why does increased dispersal ability lead to lower speciation rates?

Think about how far of a distance is required to produce allopatric populations of a species. For organisms that are poor dispersers, smaller distances will isolate them into populations that cannot stay connected via dispersal. Better dispersers can travel further distances and keep even disparate populations connected reproductively. Consequently better dispersers will be less likely to experience allopatric speciation than poor dispersers.

What is an evolutionary radiation?

An evolutionary radiation is when speciation produces many new species within a given group very rapidly (on geologic time scales, so still possibly a couple million years).

What makes an evolutionary radiation an adaptive radiation? Describe an example of an adaptive radiation.

A radiation is considered 'adaptive' when the new species are specifically adapted to particular niches within the ecosystem.

EX: Hawaiian honeycreeper birds, in which 55 species evolved from their common ancestor (European rosefinches) in about 3 million years; the different species are adapted to different food sources with accompanying morphological adaptations in their beak structure.

Pre-zygotic

prevent mating or prevent fertilization if mating occurs

Post-zygotic

prevent a hybrid zygote from developing into a viable, fertile adult

Pre-zygotic Barriers

• Habitat Isolation: species occupy different habitats, never come into contact

• Temporal Isolation: breed during different times

• Behavioral Isolation: Individuals do not recognize each other as potential mates

• Mechanical Isolation: physical differences between the organisms prevent successful mating

• Gametic Isolation: sperm is not able to fertilize the egg

Post-zygotic Barriers

• Reduced Hybrid Viability: hybrid offspring do not complete development or have low survivorship

• Reduced Hybrid Fertility: hybrid offspring are viable, but incapable of reproduction

• Hybrid Breakdown: hybrid offspring are viable and fertile, but subsequent offspring are inviable or sterile

Monophyletic

includes an ancestor and all of its descendants

Which has a larger impact on the energy available at upper trophic levels: primary productivity or efficiency of energy movement across trophic levels?

efficiency of energy transfer has a larger impact on the energy availability at higher trophic levels

Describe how the following terms relate to one another: consumption efficiency, assimilation efficiency, production efficiency, and ecological efficiency

Each of the efficiency terms focus on a particular 'step' of the process of energy movement between trophic levels.

Consumption efficiency relates to how much of the biomass available at the lower trophic level is consumed by the higher trophic level.

Assimilation efficiency focuses on how much of the biomass that is consumed is digested (and not excreted).

Production efficiency focuses on how much of the biomass that is digested is converted into biomass at the higher trophic level (and not burned for metabolic processes like respiration).

All of these together represent ecological efficiency, which is the amount of total biomass at the higher trophic level compared to the lower.

Is assimilation efficiency higher for a carnivore or an herbivore?

Carnivores. Herbivores have specialized ways of consuming food efficiently

Is the production efficiency higher for an ectotherm or an endotherm?

The loss pathway in production efficiency is primarily respiration. Endotherms have much higher respiration rates than ectotherms in order to maintain body temperatures. Consequently, we would expect ectotherms to have higher production efficiency because the loss pathway is minimized

Would you expect the consumption efficiency of primary consumers to be higher in a forest or a grassland?

The plant community in a grassland is mostly grasses, while in a forest it is mostly trees. Most organisms cannot eat wood, so the amount of plant biomass that they can consume is much smaller in a forest than a grassland. Consequently, we would expect consumption efficiency to be higher in grassland herbivores than in forest herbivores

Which has a higher production efficiency: a C3 plant or a C4 plant?

The C3 plant has higher production efficiency because it is more energy efficient. C4 plants are more water efficient, but spend more energy building sugar (because of moving CO2 into the bundle sheath cells against the concentration gradient)

Why is terrestrial net primary productivity higher in the tropics, but marine net primary productivity is higher in coastal areas?

Terrestrial net primary productivity is driven primarily by temperature (and influenced by precipitation when it is extreme). So, the tropics have high productivity because they are hot and wet.

Marine net primary productivity is driven by nutrient availability, not temperature or precipitation. Coastal areas have the highest nutrients due to runoff of fertilizer and waste products from land, and because continents drive upwelling of deep ocean currents (which contain lots of nutrients) to the surface

Is being vegan more energy efficient?

Yes, moving to a lower trophic level increases the amount of energy available to you at the trophic level you consume because lower trophic levels always contain more energy than higher levels

Describe the process that drives the oscillation in CO2 levels throughout the year

The basic driver is the global pattern of CO2 uptake from respiration and CO2 production through respiration. From ~May to ~September CO2 levels decline indicating that CO2 uptake from photosynthesis is greater than CO2 production by respiration. From ~September to ~May, the reverse is true - CO2 production is higher at this time of year


Biome driving this pattern: boreal forest since it has;

1) strong seasonality

2) high productivity (at least compared to other seasonal biomes)

3) uneven distribution between the hemispheres (because if it was evenly represented in both hemispheres, the opposite growing seasons in the North and South Hemispheres would cancel each other out)

*closer to boreal forest, the greater the oscillations are

Would you expect the timing of the peaks and troughs in the annual C02 oscillation to be the same across the globe?

Since the peaks and troughs in each location are driven by the same thing (productivity in the boreal forest), we would expect the peaks and troughs to occur at mostly the same time. There might be a bit of a delay as the changes in CO2 uptake 'trickle down'

Dead Zones

Dead zones occur when high nutrient inputs produce an algal bloom that then dies and decays, which depletes the oxygen in lower water levels to the point that many organisms suffocate

Why do dead zones commonly form at the mouth of large rivers?

They are commonly found at the mouths of large rivers because watersheds concentrate terrestrial runoff into rivers, which produces a large input of nutrients in a small area of the ocean

How is groundwater important for humans? How does the disconnect of groundwater from the global water cycle impact our future?

Groundwater is important for agricultural irrigation, especially in the Midwest United States, where 20% of our industries of corn, wheat, cotton, and beef all rely on the Ogallala Aquifer.

The fact that groundwater is 'disconnected' from the rest of the water cycle, however, means that it recharges extremely slowly, much more slowly than we withdraw water. Consequently, this source of water is increasingly difficult and expensive to access and may no longer even be accessible at any cost by 2150.

Coral Bleaching

A coral is 'bleached' if it has lost its mutualist partner, zooxanthellae. The zooxanthellae provide the color of the coral body, so their loss makes the coral white, which is the origin of the term 'bleached'

What conditions cause coral bleaching and can it recover?

Conditions that cause bleaching include warming temperatures, ocean acidification, and certain chemicals used in sunscreens (among other causes).

A bleached coral is not yet dead - it can recruit new zooxanthellae if the stressor that caused the bleaching ends and if the coral are given time to recover before a new stressor occurs.

Unfortunately, some stressors (like temperature increases) are not temporary, and individual bleaching events are occurring more and more rapidly, rarely giving coral reefs time to fully recover between events.

Describe why energy diagrams must be a pyramid

Energy diagrams must always take the shape of a pyramid (each higher level smaller than the level below it) because the primary producers (bottom of the pyramid) are the only step at which energy enters the system (through photosynthesis). At all other trophic levels, energy is lost through respiration and other forms of inefficiency, and no other energy can enter the system, producing a pyramid shape.

Does a diagrams of biomass or numbers of individuals in each trophic level have to be pyramid shaped?

No, for example a primary producer can be smaller than its primary consumer if the primary producers quickly regenerate (common for plankton)

Keystone Species

species that directly or indirectly modulate the availability of resources (other than themselves) to other species by causing physical state changes in biotic or abiotic materials, and in so doing they modify, maintain, and/or create habitats

Foundation Species

An ecosystem engineer physically alters the habitat in ways that affect the abiotic components of the ecosystem, and consequently, which species can exist in the ecosystem. Generally, ecosystem engineers increase diversity across a landscape through habitat diversification (creating patches of area they have influenced within a large landscape of unaltered habitat).

Ecosystem Engineer

species that directly or indirectly modulate the availability of resources (other than themselves) to other species by causing physical state changes in biotic or abiotic materials, and in so doing they modify, maintain, and/or create habitats

Top-down trophic cascade

A top-down trophic cascade is one in which the initial change in the system occurs near the top of the trophic levels and the impacts of the change cascade down to lower trophic levels

The example in lecture was the orca sea otter urchin kelp example.

Bottom-up trophic cascade

A bottom-up trophic cascade is one in which the initial change in the system occurs at the bottom of the trophic levels and the impacts of the change cascade up to higher trophic levels

The example in lecture was the nutrients for aquatic plants, which led to algal blooms and fish death

Latitude and Hemisphere

Positive = north
Negative = south

Tropical Rainforest

- along geo. equator around hadley cell
- high temp, high precip.
- no seasonality
- warm and wet year round

Desert

- dry, low precip.
- seasonality in temp.
- 30 degree

Temperate Deciduous Forest

- temperate = seasonal
- seasonality in temp. and occasionally getting below 0 degrees
- precip. is constant

Boreal Forest

- seasonality in temp.
- half of year below freezing
- precip. is low

Arctic Tundra

- 2/3 months above freezing
- permafrost (frozen ground)
- high latitudes

Temperate Grassland

- seasonality in temp. and precip.
- warm season is wet season

Mediterranean

- cali yeeaahh
- coasts (western)
- high seasonality in temp. and precip.
- warm season is dry season

Traits of Aquatic Biomes

- salt content (fresh or salt or in-between)

- flow and movement

- depth (how much sunlight, and more pressure)

Wetlands

- filter pollutants out of water

- critical habitat

- line of defense for storm surges

- significant loss of wetlands (cali. lost 90%)

Dispersal Methods

Spores (in the wind), as zygotes or larvae in water currents, mobile animals can disperse at any age but usually as juveniles, travel in guts of animals (snails),, in herds it can depend on age/sex, most mobile animals are restrained by major physical barriers like mountains, lakes, etc

Introduced Organism

Introduced organisms have been transported outside their native range but are not necessarily harmful

Invasive Organism

invasive species are introduced and are having negative impacts on local habitats or species

Which is more likely to become invasive, an r-selected species or a K-selected species?

An r-selected species is more likely to become invasive given their lower resource demands and high reproductive output

How are aquifers similar to other 'fossil' resources like oil and coal?

Aquifers are similar to fossil fuels in that they come out of the ground, and are very slow to replenish (so, essentially non-renewable). Aquifers are different though in that they did not form from fossil organisms (as coal and oil did)

Anthropogenic

Caused by humans

Explain Island Biogeography

The size of the island affects competition for resources so a large island will be able to support more species than a smaller island because lower competition will reduce extinction rates

The distance of the island from other landmasses affects the ease of dispersal to the island, so an island near to other landmasses will be able to support more species because easier dispersal will increase immigration rates

Any isolated or fragmented habitat may behave like an 'island' in these ways

Biocontrol

Why is this strategy difficult?

Biocontrol is a mechanism by which invasive species are controlled or eradicated from a region by intentionally introducing another organism that is a predator or parasite of the invasive species.

This strategy is difficult to implement successfully because species interactions can be unpredictable and introduce a(nother) new species to an area can have unintended consequences on the native species. In many instances, the introduced biocontrol species preys upon or parasitizes native species in addition to the invasive species without significantly reducing the impact of the invasive species.

Why is immigration rate higher when the number of species is low?

Why does immigration rate decrease as the number of species increases?

Immigration rates are higher when the number of species is low because most immigrants to the island will be new species.

As the number of species increases, individuals that are able to immigrate are likely members of species already represented on the island, so the overall immigration rate (of new species) declines.

Why is extinction rate low when the number of species is low?

Why does extinction rate increase when the number of species increases?

The extinction rate is low when the number of species is low because the degree of competition is also relatively low.

As the number of species increases, competition for resources also increases, which increases the extinction rate (Note: the island biogeography model assumes that competition is the most important species interaction, which may or may not be true in real systems)

What is represented by the point where the lines of immigration rate and extinction rate cross?

Where the lines cross is the equilibrium number of species we expect a given island to be able to support

How does the distance of an island from other nearby landmasses affect the number of species that may establish on the island?

The distance of the island to other land masses affects immigration rates; islands further from other landmasses will be more difficult to disperse to (and have lower immigration rates) and islands nearer to other land masses will be easier to disperse to (and have higher immigration rates)

How does the size of the island influence the number of species that may establish on the island?

The size of the island affects extinction rates; smaller islands will have fewer resources and higher competition (and so higher extinction rates) while large islands will have more resources and lower competition (and so lower extinction rates).

How do humans influence dispersal?

Humans generally make dispersal of organisms easier and help organisms colonize areas they would not have been able to reach on their own. Humans also take up a lot of space and so can reduce the 'size' of the island for organisms that cannot live in urban areas or agricultural lands.

Give examples of habitats that function like an island, but are not land surrounded by water

-fragmented or isolated habitat
-lakes
-mountain tops
-valleys
-fragments of forest
-Earth itself.

What was the order of major biological events?

- the origin of life on Earth
- the evolution of C3 photosynthesis
- The colonization of land by early tetrapods
- the development of fossil fuels (oil, etc)
- The evolution of C4 photosynthesis
- mass extinction (several times throughout history


a. ~3.8 billion years ago, chemosynthesizers arose probably in deep ocean vents
b. ~2.5 billion years ago in cyanobacteria; contributed our first fossil evidence of life (stromatolites)
c. The Oligocene (34-23 million years ago) in grasses
d. The Devonian (419-359 million years ago), represented by Tiktaalik
e. The organisms that produced these deposits lived during the Carboniferous (359-304 million years ago) and went extinct in the Permian Extinction (252 million years ago).
f. End Ordovician (444 mya), End Devonian (359 mya), End Permian (252 mya), End Triassic (201 mya), End Cretaceous (65 mya), and the Holocene (the present)

If they were not photosynthetic, how did the first organisms obtain sugar for respiration?

Early organisms performed chemosynthesis, which is a process by which energy rich carbon compounds are broken down for energy (instead of using sunlight)

Why did aerobic respiration arise after photosynthesis? If the first living organisms were not aerobic, how were they able to perform respiration?

Aerobic respiration arose after photosynthesis because prior to photosynthesis, there was not enough O2 in the atmosphere to make this process efficient. Prior to aerobic respiration, organisms performed anaerobic respiration or fermentation

Why do we see an increase in O2 levels following the invasion of land? What was the terrestrial landscape like at this time?

Colonizing land opens up an enormous new landscape for plants to inhabit. Not long after the initial shift to land, is when the Carboniferous period occurs, when most of Earth was covered with vast gymnosperm forests. At this time, atmospheric oxygen levels were at the highest in Earth's history

Why do O2 levels drop so significantly ~250 mya? Why do we not see similar drops 444 mya, 359 mya, 201 mya, or 65 mya?

O2 levels drop significantly at 250 million years because of the end Permian extinction which wiped out the Carboniferous era forests. The other extinctions don't appear to have affected plants as significantly as animal communities (or plants recovered more quickly than animals did), and so do not produce noticeable drops in O2

What are the different paths by which humans could have colonized the Americas?

What evidence do we use to reconstruct this migration?

10. Humans could have colonized the Americas by 1) walking across the Bering Strait land bridge from northeastern Asia to northwestern N. America,
2) Following the coast of northeastern Asia and northwestern N. America by boat,
3) crossing the south Pacific by boat (landing in S. America and moving north), or
4) crossing the Atlantic from Europe (landing in eastern North America)

Lines of evidence by which we reconstruct human migration include fossil human remains, fossil evidence of human habitation, genetic lineages and relatedness (especially in mitochondrial and Y chromosome DNA), and reconstructing the environmental landscape to evaluate what modes of transportation/migration were possible

Why is the Cambrian Period considered an 'explosion' of life?

The Cambrian is called an 'explosion' of life, because this was when animal diversity first really increased. Many of the phyla that exist today first arose during this time. We also see important behavioral changes that drive species interactions, such as predation, etc. These are very critical changes, even though recent diversification rates are higher than they were during the Cambrian

Why there is an almost exponential increase in species after catastrophes/extinctions?

This suggests that even following major destructive events like mass extinctions, the organisms that do survive are able to recolonize and repopulate the landscape (or as Ian Malcom put it so wonderfully in Jurassic Park, "Life finds a way")

Angiosperms

Flowering plants

Describe how the diversification of angiosperms in the Paleogene influenced the terrestrial environment and the diversification of other taxonomic groups.

Effects on biogeochemical cycles through increased transpiration influencing rainfall patterns, increased photosynthesis affecting atmospheric O2 and CO2 levels, species interactions with Rhizobia influencing N cycling. Also, angiosperms create two new niches for animals: nectar feeders, and fruit-eaters. As angiosperms radiate, animals that rely on nectar, fruit, or even plant tissues themselves (like the insect groups shown in the slides) also radiate.

What is the Anthropocene?

The Anthropocene is not a 'real' geological time period (meaning it has not been formally recognized by the scientific community or given a specific time range like the time periods that are shown on the big colorful map)

term to describe the time period in which human impacts have been the driving force on the global environment. It is debated when exactly that is; proposed start dates include the start of the Industrial Revolution (~1750 AD), the beginnings of agriculture in early human societies (~10,000 years ago), or the evolution of Homo sapiens as a distinct species (~300,000 years ago).

How do the following human activities drive evolutionary change in other species?

a. Hunting/fishing

b. Use of pesticides/herbicides/antibiotics

c. Urban landscapes

a. Since humans tend to prefer larger organisms, this often selects for smaller individuals and/or individuals with less impressive ornamentation (like the elk racks) and/or earlier sexual maturity

b. Use of these chemicals increases the degree to which pests are resistant to the chemicals

c. Urban landscapes have different physical components and different soundscapes. In class we looked at how bird call responds to urban sound environments (both prior to and during COVID lockdowns) and how the different types of structures in urban settings drives limb change in urban lizards

Compare and contrast the California Species of Special Concern, Endangered Species List, CITES-listed species, and the IUCN Red List.

CA SSC = State level, focused on organisms in Cali, lists only exist for herps, birds, mammals, and fish;

ESA = federal level, focused on organisms in United states, includes all taxonomic groups, managed by the Fish and Wildlife Service;

CITES = international, focused on preventing international trade of vulnerable organisms (no other protections);

IUCN Red List = international, functions similarly to the ESA, includes more 'categories' such as vulnerable, etc (ESA has only threatened and endangered)

What is the extinction vortex? What happens to a population that is in the vortex?

The extinction vortex is a process by which the negative ramifications of small population size contribute to continued reductions in population size, creating a positive reinforcement situation in which extinction of the species is inevitable. A population in the extinction vortex will go extinct

There have been five mass extinctions in Earth's history. What evidence exists that we might be in a sixth extinction? How does this extinction differ from previous extinctions?

Extinction rates of many different types of organisms have been increasing in recent years, and even species that are not yet endangered are in decline. These rates have not yet reached the threshold to consider them a global mass extinction event, but some groups are close.

What is different about this extinction is that other extinctions were caused by external abiotic factors (meteor strikes, volcanic eruptions, etc) while this one is primarily driven by another species (us)

Describe how each of the factors below threatens biodiversity

a. Habitat loss and alteration

b. Climate change

c. Invasive species

a. Reduces the overall habitat available to species, which can directly reduce population size, can also increase fragmentation of remaining habitat exacerbating the population decline.

b. Can reduce overall habitat available to species and can shift the geographic location of suitable habitat to areas that species may or may not be able to access.

c. Can reduce diversity in ecosystems by outcompeting or preying upon/parasitizing native species.

What is the primary goal of California's 30x30 initiative? Are we on track to meet this goal?

The goal of 30x30 is to protect 30% of California's land area and coastal waters by the year 2030. Currently, the state has protected 24% of its land area and 16% of its coastal waters. If the current trends of identifying and protecting area continue, we likely will achieve this goal

Fragmentation of habitat is a major problem for conservation. What strategies have been used to reduce fragmentation of remaining habitat? Phrased another way, how do conservation land managers increase connectivity between habitats?

Some mechanisms for increasing connectivity and reducing fragmentation include:

a. Design of reserve lands: larger reserves, located closer together, with protected corridors between them, with limited edge (more compact in shape) and surrounded by buffer zones

b. Wildlife corridors across human impacted landscapes, especially highways

c. Removal of human constructed barriers, such as dams

Allele H-W Formula

p + q = 1

Population H-W Formula

p^2 + 2pq + q^2 = 1

What is H-W?

Null hypotheses

Founder Effect

genetic drift that occurs after a small number of individuals colonize a new area

Bottleneck Effect

a reduction in the genetic diversity of a population caused by a reduction in its size

How are the founder effect and a population bottleneck similar?

How are they different?

Which one would you predict to have a more serious negative impact on the species as a whole?

Both are a reduction in the gene pool of the population under consideration through reduction in population size.

The major difference is that for a founder event, the larger original population still exists and can maintain genetic diversity (and possibly contribute it to the founder population through migration).

In a bottleneck event, the small population is all that remains and whatever genetic diversity is (or is not) present there is all the species as a whole as left. Consequently, the bottleneck is more likely to have severe negative consequences for the species.

What are the consequences of genetic drift?

Genetic drift causes an overall reduction in genetic diversity (through loss/fixation of alleles), increases in inbreeding, increases in homozygosity, increases in deleterious recessive conditions, increased susceptibility to future stressors like disease or climate change.

Why are small populations more affected by drift than larger populations?

Small populations are more affected because there are fewer 'chances' for rare alleles to get passed on

Gene flow and genetic drift are sometimes referred to as 'non-adaptive evolution.' What does this phrase mean?

Non-adaptive means it is genetic change that does not (necessarily) benefit the species' ability to survive and/or reproduce

What type(s) of evolution is/are adaptive?

The only type of evolution that is adaptive is natural selection because this is the only one that selects geno/pheno that are beneficial in the environment.

All other changes are completely or partially random and may negatively impact the population. For example, in small populations, genetic drift can be so powerful as to increase the frequency of deleterious alleles even when natural selection is working to decrease them.

Describe the genetic mechanism by which inbreeding increases homozygosity in a population.

In full inbreeding, individuals with similar geno/pheno mate only with one another. Matings between homozygous dominant individuals will always result in homozygous dominant offspring and matings between homozygous recessive individuals will always result in homozygous recessive offspring.

Mating between heterozygotes produces 50% heterozygous offspring, 25% homozygous dominant and 25% homozygous recessive - so each generation, half of the heterozygote population shifts into the homozygous populations and eventually all heterozygotes are lost.

How might natural selection affect the fate of a new mutation in a population?

If the allele is beneficial, natural selection might cause it to increase in the population, while if the mutation is deleterious, natural selection might cause it to decrease. Regardless of its
beneficial/deleterious status, genetic drift might cause the mutation to be lost in the next generation. It could be transmitted to other populations via migration. If the mutation affects the individual's reproductive biology, it may affect randomness of mating (by making the carrier more or less attractive to mates, capable of mating, etc)

Natural Selection Conditions

1. population must be reproducing

2. individual in population must vary in their traits

3. trait must be heritable

4. individual with different traits must have differential success

H-W Conditions

- no mutation

- no natural selection

- no genetic flow (no migration)

- no genetic drift (requires infinitely large pop. size)

- random mating

Stabilizing Natural Selection

Phenotypes nearest the mean have the highest fitness. The mean stays the same, variation is reduced

Directional Natural Selection

Phenotypes at one extreme have the highest fitness. Mean trends toward the extreme.

Disruptive/Diversifying Natural Selection

Phenotypes at both extremes have higher fitness than the mean. Variation is increased, bimodal pattern emerges.

Frequency-dependent selection

Rare phenotype has the highest fitness. Frequency of phenotypes oscillate.