BIOL 300: Exam 4, Module 14: Evolution

Microevolution

Small changes that occur within a population from one generation to the next OR changes in gene frequency of a population over time

Macroevolution

Applies microevolution to a long time scale to explain how new species originate and evolve.

Genotype

The genetic makeup of an individual.

Phenotype

The physical appearance and actual behavior of an individual, resulting from the interaction between genotype and environment.

Population

all of the members of a particular species in a particular area

example: otters in Monterey Bay

Gene pool

All of the alleles in a population. Alleles are different versions of a gene.

example: straight vs. curly hair

Gene frequency

The percentage of each allele in a population.

Genetic diversity

How much genetic variation exists within a population.

Speciation

The process of two populations becoming two distinct species.

example: ensatina salamanders in california

Reproductive isolation

Two populations can no longer produce viable offspring.

example: lions and tigers are unable to mate due to ecological isolation (they do not live in the same habitats)

Consilience

the concept of uniting different fields of knowledge by linking facts and theories across disciplines to create a common understanding.

Describe the pattern and process of the theory of evolution

The overall pattern of evolution includes the observation that living organisms change over time. This change accumulates, leading to the diversity of life we see today. All organisms are believed to descend from a common ancestor. Over long periods, these changes can result in the formation of new species (“speciation”). Evolutionary change can occur gradually or in periods of rapid change interspersed with longer periods of stagnancy.

The primary process driving evolution, as proposed by Charles Darwin and Alfred Russel Wallace, is Natural Selection

List the observations that led to development of theory of evolution.

•Variations exist among individuals within a population.

•Species produce more offspring than can be supported by the environment.

•Traits are inherited from parents to offspring.

•Limited resources mean organisms must compete to survive.

•Earth is way older than 6,000 - 10,000 yrs old

What is the species problem?

Where did all 10 million species come from?

How old is the Earth?

4.5 billion years old

Explain the theory of evolution and how natural selection works.

Darwin and Wallace concluded that certain individuals are better adapted to their environment. These advantageous traits then spread through the population over generations. This results in individuals with greater reproductive success being favored, aka "Survival of the fittest," where fitness relates to survival and reproduction. Environmental conditions create selective pressures that favor organisms with traits that increase their fitness. Natural selection acts on the phenotype (the physical appearance and behavior), and the associated genotype (the genetic makeup) is carried along with it.

Explain what is meant by modern evolutionary theory/modern synthesis.

Modern Evolutionary Theory combines:

Darwin and Wallace’s ideas + modern genetics

What are the three patterns of natural selection?

Natural selection can follow different patterns:

directional selection favors individuals at one extreme of a trait, disruptive selection favors individuals at both extremes, and stabilizing selection favors intermediate phenotypes

What is the main difference between the biological and morphological definitions of a species?

The biological definition of a species focuses on the ability of organisms to reproduce and produce viable offspring, whereas the morphological definition relies on similar physical characteristics.

Provide one example of direct observation of natural selection given in the material

One example is the development of drug-resistant bacteria, like the strain of gonorrhea that is no longer susceptible to antibiotics.

Describe what adds genetic variation from a population.

•Mutations are changes in the DNA of an organism that are passed on to offspring.

•Recombination occurs through sexual reproduction and produces new combinations of alleles. While not creating new alleles itself, it shuffles existing ones into new combinations, contributing to the overall variation in genotypes.

•Gene flow is the movement of organisms from one population bringing their alleles into a different population. This adds genetic variation to the recipient population

Describe what removes genetic variation from a population.

•Natural Selection can lead to certain alleles becoming more common while others become less common or are lost from the population, thus potentially reducing overall variation for those traits

•Genetic Drift refers to random changes in the gene frequency of a population. These random changes can cause alleles to be lost from the gene pool

•Sexual Selection where mates often prefer specific traits, reducing variation in traits passed to offspring.

•Artificial Selection is natural selection replaced by human preference. By selecting specific traits, you reduce gene diversity.

•Gene Flow can also reduce the genetic differences between populations over time by mixing their gene pool

Define adaptation; list the three kinds.

adaptations = traits that increase an organisms fitness in the environment.

1. physical

2. behavioral

3. physiological

Describe the steps of allopatric speciation

1. One population becomes geographically isolated from the others

2. Geographic isolation prevents gene flow between populations. Gene flow occurs when organisms from one population bring their alleles into a different population.... The absence of this movement keeps the gene pools of the separated populations from mixing.

3. Natural selection acts on both populations independently due to different environmental conditions.

4. Small changes accumulate in each isolated population over time until they are reproductively isolated and are considered two distinct species

Describe the steps of speciation

Speciation requires reproductive isolation. This means that the two populations can no longer reproduce viable offspring. Reproductive isolation acts as a barrier that prevents gene flow between the diverging populations, allowing them to accumulate differences independently

What are the 2 main types of reproductive isolation

pre- and post-zygotic

Define and explain the process of prezygotic reproductive isolation

Prezygotic reproductive isolation occurs because the sperm and egg never meet because:

◦ Organisms are in different habitats.

or;

◦ They have different activity patterns

or;

◦ They meet but do not actually mate

what are the 5 types of prezygotic reproductive isolation

• Ecological

• Mechanical

• Temporal

• Behavioral

• Gametic

Ecological isolation

males and females of different populations live in different regions

example: lions and tigers

Mechanical isolation

the sex organs of one species do not fit into the vagina of another species

ex: righthanded snails can only mate with other righties

Temporal isolation

two species are active at different times of the day or year

example: eastern spotted skunks mate at different times of the year than western spotted skunks

Behavioral isolation

females of one species are not attracted to males of another species

example: the mating calls of tri-colored blackbirds will not attract a red-winged blackbird.

Gametic isolation

the sperm and egg are not genetically compatible and thus do not fuse

example: white Lophelia (deep sea coral) cannot reproduce with white Madrepora (another coral)

Define and explain the process of Postzygotic reproductive isolation

Postzygotic reproductive isolation occurs when reproduction is attempted but:

◦ It is unsuccessful

or;

◦ The offspring are sterile, i.e. cannot reproduce

what are the 2 types of postzygotic reproductive isolation

• hybrid infertility

• hybrid inviability

hybrid infertility

Hybrid infertility: Resulting hybrids cannot reproduce.

example: when a horse (2n=64) and donkey (2n=62) mate, they create a mule (2n=63) which cannot reproduce due to its haploid number

hybrid inviability

Hybrid inviability: The hybrid does not survive to adulthood

example: a yellow-bellied toad and a fire-bellied toad reproduce but it will not last to adulthood due to mismatched genes

Misconceptions about evolution

•Evolution is not goal-oriented, meaning that organisms are not slowly striving towards a predetermined perfect form.

•Natural selection cannot create a "perfect" organism. There are imperfections in any organism. Natural selection favors organisms that are the best fit for their current environment to survive and reproduce.

•Individuals do not evolve. Natural selection acts on the individual, resulting in evolution acting on the population

•Natural selection does not provide organisms with what they "need". It acts on existing variation within a population, it doesn't generate traits on demand

what can serve as evidence for the Theory of Evolution by Natural Selection?

• direct observations

• fossil records

• homology

• embryology

• vestigial structures

• analogous structures

• biogeography

• artificial selection

Explain the 2 types of homology

Physical homologies: similar structures of a common ancestor

example: the forearms of birds, bats, dogs & humans are structurally similar

Molecular homologies: similarities in DNA, RNA, etc.

example: chimps and gorillas have very similar DNA to humans

Embryology

This is the study of how organisms develop. Embryology can reveal physical homologies that are not visible in adult organisms. example: the presence of gill structures in embryos

Vestigial structures

features in an organism that have no current function but served a purpose in their ancestors.

examples: eyes in blind cave fish / wings on ostriches

Analogous structures

similar physical structures due to similar environments and selective pressures (aka “convergent evolution”).

Biogeography

the study of geographic distribution of species.

example: tectonic plates

example: islands, for instance, often have many unique species, but these species are typically most similar to the species found on the closest mainland, suggesting colonization and subsequent diversification

artificial selection

When natural selection is replaced by human preference; farmers and breeders can selectively breed organisms with desirable traits.

• Corn

• Domesticated dogs that originated from wolves