AP biology unit7

Natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

directional selection

one of the extremes are favored

disruptive selection

both of the extremes are favored

stabilizing selection

the majority is favored

heterozygote advantage

since you have both alleles, you can pass on the favorable one to your offspring so they will be successful

sexual selection

natural selection arising through preference by one sex for certain characteristics in individuals of the other sex

genetic flow

transfer of alleles or genes from one population to another, migration and emigration can causes this

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

bottleneck effect

some type of catastrophe wipes out a large segment of a population and survivors are not a representation of the original population

mutations

create new alleles, advantageous alleles will increase over generations

divergent evolution

one species goes 2 different way and becomes 2 different species, usually due to environment changes

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

parallel evolution

Two related species that have made similar evolutionary adaptations after their divergence from a common ancestor

Allopatric (geographic isolation)

A type of reproductive isolation due to separation by an impassable geographic barrier such as a mountain range, body of water, etc.

behavioral isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

mechanical isolation

reproductive parts do not fit

sterile offspring

reduced hybrid fertility (offspring cannot reproduce- postzygotic) i.e. mule

hybrid inviability

offspring dies during development (postzygotic)

hybrid breakdown

Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile

Hardy-Weinberg equilibrium

condition in which a population's allele frequencies for a given trait do not change from generation to generation

descent with modification

principle that each living species has descended, with changes, from other species over time

phylogenetic tree (or cladogram)

a diagram that depicts the ancestral relationships between organisms

explain differential reproductive success as it relates to the struggle for existence

more successful you are at reproducing, the more you will pass on your genes and your offspring will be fit

explain what the statement "natural selection depends on time and place" means

what traits are passed on depends on the environment and it takes generations for natural selection to take effect

homologous structures

Structures in different species that are similar because of common ancestry. Same structure, different function

Analogous structures (convergent evolution)

various structures in different species having the same function but have evolved separately, thus do not share common ancestor

How are the founder effect and the bottleneck effect the same, yet different?

the founder effect and the bottleneck effect are the same because the number of organism within a population changes and the frequency of a population changes but they are different because the founder effect happens when emigration or immigration occur and the bottleneck effect happens when a catastrophe wipes out a segment of a population

What 5 conditions must be met for a population to be in Hardy-Weinberg genetic equilibrium?

1. no mutations

how can gene flow affect genetic equilibrium in a population

if more organisms come or more leave, then there can be more organisms or less organisms and can change the frequency of alleles and effect equilibrium

how does the term differential reproductive success relate to natural selection

if you are more successful at reproducing then natural selection will be successful and the offspring will be fit

Describe how selection pressures can change allelic frequencies.

if there is a catastrophe and you are only able to mate with an organism with certain genes, then the allelic frequencies will change because then there will be more of one gene and less of another

Can an individual organism adapt to its environment?

no because if an organism is not born with the genes then it can not make a gene in order to survive, only a population can adapt because mutations can occur and then will pass that gene along and then adaption will occur

Why do vestigial structures disappear over time?

because organisms that have that harmful structure will not mate and the structure will be lost

What types of evidence can be used to determine common ancestry?

1. structural evidence (homolgous, analogous, and vestigial) structures

allopatric speciation

new species is created due to geographic barriers

sympatric speciation

new species is created within the orginial population

how can allele frequencies change over time

1. mutations occur

name 4 things that cladograms show

1. number of shared characteristics

how did Darwin explain the diversity of like on the Galapagos

1. overproduction

what did darwin notice about the animals on the south american continent

-they looked like they should in the environment that they live in

what did darwin notice about the organisms on the Galapagos

-some were similar to mainland organisms

natural selection acts on ___, not ____

populations not individuals

natural selection acts on frequencies

gene

Hardy-Weinberg equation

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

Vistigual Structures

A structure that is no longer needed (i.e. hipbones in whales, wisdom teeth in humans, goosebumps in humans)

Charles Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

Evolutionary fitness

a measurement of the degree to which an organism can successfully adapt to its environment and can reproduce fertile offspring

Selective pressures

forces in the environment that influence reproductive success in individuals

Artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

Adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species to diverse group of species quickly.

founder effect (genetic drift)

Gene pool dependent on the first individuals to settle in a location.

Is natural selection a random event?

No, it is not random.

Which population is more susceptible to environmental impacts, and thus, natural selection? Small or large?

Small

How can fossils be dated?

1) by examining the age of the rocks where the fossil was found.

What cellular structures do all eukaryotic organisms have in common? What does this imply?

membrane-bound organelles, linear chromosomes, genes that contain introns; implies common ancestry

Do populations continue to evolve?

Yes

Explain antibiotic resistance in terms of evolution.

Bacteria grow within their environment. When they become too big in population size or harmful, doctors prescribe antibiotic medicine. The medicine kills most bacteria in the population. However if not all medicine is taken as prescribed, some bacteria survive. The surviving bacteria are resistant to the medicine and pass on those traits to new bacteria via reproduction (binary fission and plasmid exchange). The new population that grows are resistant to the medicine (unlike the original population).

Describe conditions in which new species arise.

via reproductive isolation.

Punctuated equilibrium

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

Gradualism

The theory that evolution occurs slowly but steadily

Prezygotic barriers

Barriers that impede mating or hinder fertilization.

Postzygotic barriers

Barriers that prevent the hybrid zygote from becoming a fertile adult.

Extinction

A term that typically describes a species that no longer has any known living individuals.

Can human activities lead to species extinction?

Yes

How does species extinction lead to evolution?

Extinction of species opens up new habitats or niches for living species to exploit. Species that take advantage of these new niches tend to experience adaptive radiation, and thereby, allowing evolution and a greater biodiversity to occur.

Environmental perturbation

Changes in environment affecting species survival.

abiogenesis

The idea that long ago, very simple life forms spontaneously appeared through chemical reactions.

hydrothermal vent theory

Life developed around hydrothermal vents in the ocean using chemosynthesis instead of photosynthesis

Primitive earth environment

hot and anaerobic, with a lot of volcanic activity; no free oxygen/low oxygen

Panspermia Hypothesis

• Earth is continuously bombarded with material from interstellar space, much of it consisting of organic compounds.

Miller-Urey Experiment (1953)

demonstrated that organic compounds could be made by simulating conditions on early Earth

RNA World Hypothesis

Hypothesis that describes how the Earth may have been filled with RNA-based life before it became filled with the DNA-based life we see today.