Darwinian Evolution + Population Evolution

Define “descent with modification”

Evolution; used to summarize the process undergone by species in which they accumulate differences from their ancestors

Evolution was not darwin’s theory, what did he contribute to it?

Darwin proposed the theory of natural selection (“survival of the fittest”), which suggests that certain organisms have better biological fitness due to the favorable adaptions they inherited

Distinguish between Lamarck and Darwin’s evolutionary theories

Lamarck belived that the “use and disuse” of aquired traits could lead to a species’ offspring inheriting them. His theory is incorrect but important because he was one of the first to acknowledge that evolutionary processes occur. Darwin proposed “survival of the fittest” and “descent with modification”, meaning that species adapted over time and had variations that increased their survival rates.

Define Biological Fitness

An organism’s ability to survive and reproduce fertile offspring

How did darwin’s observation of finches influence his theory of natural selection?

The variation in the finches’ beaks despite the fact that they all originated from the same land showed that they adapted and evolved to suit their biological niches

How do finches’ beaks offer supportive evidence for evolution

Their differences allowed for them to succeed in the environments they were in as they allowed them to eat the food in that specific area. This shows adaptation and evolution in traits

What is artificial selection

Selection altered by humans due in an attempt to cause favorable traits to occur

What are some evidence for evolution?

Paleontology: Physical remnants of organisms and transitional fossils show how organisms evolved over time

Biogeography: Geographic spread of organisms provide evidence for their evolution; Differences in geography lead to new species

Insecticide Resistance/Drug Resistance: Resistance is built because individuals with lower resistance are wiped out leading to ones with higher resistance reproducing and using this trait to evolve

Homologous Structures: A structure can be ancestral to multiple organisms and modified for different uses, indicating evolution

Vestigial Organs: Organs that used to play a role in an organisms’ life but no longer do that are proof that organisms’ population had undergone evolution

Embryology: Embryos are very similar during early stages, suggesting that animals have evolved from a common ancestor

Biochemistry: The basic similarities of ALL living things suggests a common ancestor

Define convergent evolution

When environmental pressures and natural selection produce similar traits in organisms in species with different evolutionary lineages

Define species

A population or group of populations in which members have the potential to interbreed and produce fertile offspring

What conditions are thought to be essential for the formation of distinct species

Isolation and Reduced Gene Flow because Reduced Gene Flow allows for differences in populations and thus speciation

What are the two types of reproductive isolation barriers?

Prezygotic: Before the zygote is formed

Postzygotic: After the zygote is formed

Prezygotic Barriers and Examples

Geographic Isolation: A geological or climate change that splits an originally single population (Darwin’s Finches)

Temporal Isolation: When species mate at different seasons or times cause them to not reproduce (Frogs mating in the spring vs. summer)

Behavioral Isolation: When species’ mating practices or behaviors do not match (Birds only responding to certain bird calls)

Mechanical Isolation: When species are morphologicallt unfit to reproduce together (Different dog breeds being unable to undergo reproductive processes together)

Gametic Isolation: When the gametes of one species cannot form a zygote with another’s (Red vs. Purple Urchins

Postzygotic Barriers and Examples

Hybrid Inviability: When a hybrid species does not live to reach reproductive age (Hybrid Tadpoles that die before becoming frogs)

Hybrid Infertility: When a hybrid species is unable to reproduce at all (Mules being completely infertile)

Hybrid Breakdown: When the first hybrids can, but the second hybrid generation is unable to reproduce (Copepod hybrids have lower survival and reproductive rates)

Allopatric vs. Sympatric Speciation

Speciation that occurs due to geographic barriers being formed is allopatric; Speciation that occurs within the same area as the original population is sympatric

How can polyploidy lead to speciation?

Polyploidy’s changing in chromosome numbers can create reproductive isolation because new traits in selective breeding can impede organisms from breeding with their diploid ancestors

Gradualism vs. Punctuated Equilibrium

Gradualism is proposed as a slow, gradual process of evolution; Punctuated equilibrium suggests that evolution consists of long, stable periods followed by bursts of rapid evolution

Why is genetic variation important to evolution?

Genetic variation allows for traits to be favored, leading to natural selection and the evolution of populations

Describe what is meant by…

“Natural Selection cannot produce perfect organisms”

“Not all evolution is adaptive”

“Selections can only edit existing variations”

“Natural Selection cannot produce perfect organisms” - Environmental changes and constraints alter the favorable traits in a population, so organisms can never be flawless

“Not all evolution is adaptive” - Several evolutionary mechanisms, such as mutations, are not always beneficial to a species

“Selections can only edit existing variations” Natural selection works with favorable traits, not creates new ones

What is the primary mechanism responsible for evolutionary change

Natural Selection “survival of the fittest”

How does genetic drift differ in the founder’s and bottleneck effect?

The founders effect is when individuals isolate themselves from a larger group and thus form new populations. The bottleneck effect is when environmental change or human inerference causes a reduce in a population, leading to the effect of chance events