Chapter 10: Evolution Flashcards Preview

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Flashcards in Chapter 10: Evolution Deck (44):


The change in allelic frequencies within a population.


Methods to Date the Earth's History

- Radiometric dating.
- Paleomagnetic dating.
- Studying fossils and sedimentary rock layers.


Cambrian Explosion

The sudden appearance of many present-day phyla.


Evidence for Evolution

1. Fossil Record: Using radioactive dating and half lives, we can wee how old a fossil is. This is evidence that many of the species once on earth already went extinct.

2. Comparative Anatomy: we can compare similar structures between species to determine if they are evolutionary related or not.

3. Comparative Biochemistry: Evolutionarily related species will exhibit the same or very similar biochemical pathways.

4. Comparative Embryology: Evolutionary related species will exhibit the same or similar embryonic development.

5. Molecular Biology: Comparison of the cytochrome c. sequence (all organisms have this). Similar organisms will have similar or identical sequences.

6. Biogeography: the continental drift change the Earth's flora and fauna. This often changes the distribution of life on Earth.


Analogous Structures

Same structure on two species that results due to a similarity in selection press, and is an evidence of evolution.


Homologous Structures

Same structure on two species that results due to a common ancestor between the two.


Vestigial Structures

A structure that is no longer necessary and plays no useful role in the functioning of the organism, and thus is evidence of evolution.



Specialized in taxonomy, and created the binomial naming system.



Stated that each time period had characteristic fossils, which were caused by a series of catastrophes.



Proposed the idea of gradualism: Earth changes over time, gradually.



Proposed a wrong theory of evolution. Stated that individuals could inherit acquired characteristics from their ancestors through use and disuse.



Came up with the same theory of natural selection as Darwin.


Charles Darwin

On his trip to the Galapagos Islands, Darwin created his theory of natural selection and the descent with modification. Published his book "On the Origin of Species."


Darwin's Theory of Natural Selection

1. Populations tend to overgrow.
2. This overpopulation leads to competition for resources.
3. Some individuals are more "fit" to reproduce and pass on its genes than others.
4. Only the most "fit" live on to survive and reproduce.
5. This leaves an increasingly advantageous population.


Selective Advantage

An advantage certain individuals have against their environment's selection pressures.


Stabilizing Selection

Eliminates the extremes and favors the middle ground organisms. An example includes baby weight – middle weight babies are more likely to survive than very light or heavy babies.


Disruptive Selection

Favors the two extremes of a population. Might result in balanced polymorphism, or the creation of two distinct species. An example includes light and dark mice in light and dark rocks.


Balanced Polymorphism

When a species is separated into two types.


Directional Selection

Favors only one extreme in a population. An example includes dark and light moths in England. At first, light moths had the advantage. However, when England was covered in soot and smoke, the dark moths the received the advantage.


Sexual Selection

Selection in competing or attracting mates.


Sexual Dimorphism

Differences in appearance between males and females.


Artificial Selection

Humans tamper with normal mating by purposely breeding two organisms to get favorable traits.


Methods to Preserving Variation in a Population

1. Balanced Polymorphism: Presence of two or more phenotypically distinct forms of a trait (dark mice and light mice).
2. Geographic isolation: difference in phenotype due to different selection pressures in a species.
3. Sexual Reproduction: Variation due to the shuffling and recombination of parts of chromosomes (independent assortment, crossing over, random mating).
4. Outbreeding: mating of organisms with someone not closely related to get a wide gene pool (opposite of inbreeding).
5. Diploidy: maintains and hides a huge pool of alleles.
6. Heterozygote Advantage: sometimes the hybrid will have selective advantage over the homozygous individuals, which retains more alleles.
7. Frequency-dependent Selection: Decrease in the frequency of common phenotypes, and increase in the frequency of rarer phenotypes.
8. Evolutionary Neutral Traits: Traits that seem to have no selective advantage over the other (ex: human blood type).


Genetic Drift

Change in the gene pool due to chance.


Bottleneck effect

Natural disasters greatly reduce the size of the gene pool unselectively, which causes a loss in genetic variation. Some alleles are then over or under represented in this new modified population.

An example includes elephant seals being hunted almost to extinction until the government placed regulations over hunting. When the population grew back, the genetic variation is very small.


Founder effect

A small part of the population moves away to a new area, in which the gene pool is probably not representative of the original one.

An example includes a group of Amish people moving to a new area, and one of the members had the rare trait for polydactyly. This resulted in this close community having a high incidence of polydactyly.


Gene Flow (Causes of Evolution)

Movement of alleles in and out of a population.


Mutations (Causes of Evolution)

Changes in genetic material that leads to an increase in diversity.


Nonrandom Mating (Causes of Evolution)

Organisms choose their mate due to the concept of survival of the fittest, which eliminates the less fit individuals.


Natural Selection (Causes of Evolution)

Survival of the fittest leads to only the most fit individuals passing their genes onto the next generation.


Characteristics of Hardy Weinberg Equilibrium

1. Large populations.
2. No natural selection
3. No immigration
4. Random mating
5. No mutations.



A population whose members have the potential to interbreed and produce viable, fertile offspring.



The diverging of one species into two, due to genetic differences.


Allopatric Speciation

Caused by geographic isolation, such as separation due to mountains, canyons, etc. An example is the Grand Canyon squirrels.


Sympatric Speciation

Speciation that occurs without geographic isolation. Causes include:

Polyploidy: polyploidy is when a cell has more than two sets of complete chromosome. Polyploid organisms cannot breed with non-polyploid organisms.

Habitat Isolation: Where two organisms live in the same place but rarely encounter each other.

Behavioral Isolation: mistakes and differences in mating rituals will prevent mating.

Temporal isolation: Difference in timing that prevents mating

Reproductive isolation: a variety of reasons. One includes incompatibility of the genitalia.


Prezygotic barriers

Barriers that impeded the mating of two organisms.


Postzygotic barriers

Barriers after the mating has occurred, which stop the zygote from being developed.


Divergent Evolution

When a population becomes separated and faces a new set of selection pressures which evolves into a new species. Allopatric and sympatric speciation are examples.


Convergent Evolution

When similar selection pressures result in very similar adaptations. Based on analogous structures.


Parallel Evolution

Evolution that occurs from evolving from a common ancestor, then experiencing similar selection pressures that result in similar adaptations.



When an adaptation in one species causes an adaptation to a related species. Examples include predator-prey, parasite-host, competitive, and mutualistic species. For example, an evolutionary change in the morphology of a plant might cause a change in the organism that eats that plant.


Adaptive Radiation

Emergence of many species from a common ancestor to fill an ecological niche. Examples include the Darwin's finches on the Galapagos Islands.



The theory of evolution that states evolution occurs in a series of small steps and transitional phases.


Punctuated Equilibrium

The favored theory of evolution, in which new species emerges suddenly after long periods of stasis.