AP BIO First semester

Evolution

General descent with modification/change over time 2) Change in genetic composition of a population from generation to generation

Natural Selection

How evolution happens (the mechanism)

Observation 1 of natural selection

Members of a population often vary greatly in their traits

Observation 2 of natural selection

Traits are heritable from parents to offspring

Observation 3 of natural selection

Species produce more offspring than their environment can support

Observation 4 of natural selection

Because resources are limited, not all offspring that are born, survive

inference 1 of natural selection

Individuals with heritable traits that help them survive/reproduce leave more offspring (traits depend on environment)

inference 2 of natural selection

This unequal reproductive success leads to the accumulation of favorable traits in the population over generations

Adaptation

inherited characteristic that increases an organism's chance of survival and reproduction in specific environments

What are Key Ideas about Natural Selection and Evolution?

Individuals don't evolve; populations do Traits/characteristics/adaptations don't just appear when needed "Good" or "Bad" characteristics/traits depend on environment Evolution doesn't head towards a goal/perfection Evolution doesn't always cause organisms to go from simple to complex Humans aren't separate from/or above other living things

Macroevolution

Big evolutionary changes over long time scales @ the species level or above

Microevolution

Small evolutionary changes over a few generations within a single species

Variance

S^2 = (Sum(x - mean)^2)/(n-1)

Standard Deviation

Square root of the variance

Standard Error

SE = s/sqrt(n)

Graphing SE

2x SE drawn above and below the mean (error bars)

What is the evidence for evolution?

Homology Fossil Record Biogeography Direct Observation

Homology (Evidence for Evolution)

Similarities resulting from common ancestry

Types of Homology

Anatomical Homology Developmental Homology Molecular Homology

Homologous Structures

Structures in different species that are similar because of common ancestry (ie arm/hand bones in cats, bats, humans, whales)

Vestigial Structures

Homologous structures that are present in an organism but are no longer used (ie human tailbones)

Convergent Evolution

When organisms adapt to similar environments in similar ways (not bc of common ancestry); results in analogous structures

Analogous Structures

1)Features of different species that are similar in function but not necessarily in structure Do not derive from a common ancestral feature Evolved in response to a similar environmental challenge.

Developmental Homology

Comparative embryology; Reveals anatomical homologies not visible in adult organisms (ie embryos)

Molecular Homology

Similarities in DNA or amino acid sequences due to common ancestry; closely related organisms have similar DNA

Fossil Record (Evidence for Evolution)

Provides evidence of the extinction of species, the origin of new groups, and changes within groups over time Can determine extinctions, transitional forms, ancestors of living species

Geological Timescale

Can determine age of fossils based on rocks, relative strata/layer, chemical dating methods

Biogeography (Evidence for Evolution)

How species are distributed across geography; closely related species are usually found near each other

Direct Observation (Evidence for Evolution)

Observable, measurable changes over short periods of time

Artificial Selection

when humans select for particular traits

Continuous Data

No categories or discrete measurements (ie height of plants, weight of students)

Discrete Data

Counts or categorical; data points are fixed (ie number of students, number of plants)

Null Hypothesis

The counter to a hypothesis; can be tested statistically (ie there is no statistically significant difference between my x and y groups)

Chi Squared Analysis

"Goodness of Fit" Test; How well does your data fit experimental expectation; is your null hypothesis supported?

Accepting Null Hypothesis

If the X^2 value is LESS than the critical value, that means your observed/expected values are not significantly different from each other

Reject Null Hypothesis

If the X^2 value is MORE than the critical value, that means your observed/expected values are significantly different from each other

Relative Fitness (Modes of Selection)

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals (survive, have babies, babies survive and have babies)

Directional Selection

Conditions favor individuals exhibiting 1 extreme of the trait/phenotype (skewed data distribution)

Stabilizing Selection

Conditions favor the intermediate phenotype, both extremes are selected against (symmetrical distribution)

Disruptive Selection

Conditions favor individuals at both extremes of the phenotype over individuals with intermediate phenotypes (bimodal graph)

Sexual Selection

Certain traits increase mating success

Intersexual Selection

One sex chooses mates of the other sex based on certain characteristics (ie looks, calls)

Intrasexual Selection

Members of the same sex compete with each other for access to the other sex (ie fighting, intimidation)

Sexual Dimorphism

Difference in size or appearance between sexes of the same species

Artificial Selection

Humans, rather than nature, choose desirable traits in organisms and breed individuals together based on those traits (ie strawberries, dogs, pets)

Taxonomy

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (Dumb Kings Play Chess On Fine Green Sand)

Biological Species Concept (BSC)

A group of individuals capable of interbreeding and producing viable, fertile offspring

Issues with BSC

Fossilized Organisms, Captivity vs. Wild, Molecular Measures, Asexually reproducing species

Allopatric Speciation (other land)

When a population is divided by a geographic barrier (river, highway, canyon) and no interbreeding occurs between the separated groups. The gene pool gradually changes through separation until eventually the groups are so different that they would not reproduce

Sympatric Speciation (same land)

One species becomes two or more while living in the same geographic region. Happens via reproductive isolation

Reproductive Isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring via Pre-zygotic Isolation and Post Zygotic Isolation

Pre-zygotic Isolation Types

habitat, temporal, behavioral, mechanical, gametic isolation

Habitat Isolation

(Ecological Isolation) Live in the same region, don't encounter each other

Temporal Isolation

When 2 species mate at different times of day/season

Behavioral Isolation

Unique behaviors identify and attract some species

Mechanical Isolation

Male and female sex organs are not compatible

Gametic Isolation

Egg and sperm (gametes) don't fuse into a zygote

Post Zygotic Isolation

Reduced Hybrid viability, fertility, and breakdown

Reduced Hybrid Viability

Hybrids fail to develop/be born

Reduced Hybrid Fertility

Hybrids cannot reproduce

Hybrid Breakdown

Hybrids are viable and fertile, but their offspring are feeble or sterile

Speed of Speciation

(It Depends)

Gradualism

Evolution proceeds chiefly (slowly) by the accumulation of gradual changes Rate of speciation is constant

Punctual Equilibrium

Evolution has periods of rapid speciation and long periods of no change Rate of speciation not constant

Adaptive Radiation

Many new species diversify rapidly from a common ancestor tends to happen when an environmental change leads to new environmental resources and niches

Node

Points on a cladogram that represent a common ancestor can rotate branches at a node

Monophyletic

Includes the most common ancestor of all selected organisms and all of the descendants of the most recent common ancestor

Paraphyletic

Includes the most recent common ancestor of all selected organisms but does not include all the descendants of the most recent common ancestor

Polyphyletic

A group of organisms in which the most recent common ancestor is NOT included

Outgroup

An organism not belonging to the group whose evolutionary relationships are being investigated

Genetic Drift

Chance events that can cause Allele frequencies to fluctuate from one generation to the next (usually associated with small populations) driven by chance and small population size

Gene Flow

Individuals emigrating from one population and immigrating to another

Species

Can interbreed in nature and produce viable, fertile offspring Species can have many populations

Population

A group of individuals of the same species that live in the same area

Founder Effect

When a few individuals become isolated from a larger population and establish a new population New population may differ in genetic diversity from the source population This is a specific type of genetic drift

Bottleneck Effect

A severe drop in population size By chance alone, certain alleles may be over/underrepresented Population will increase on the other side of the bottleneck but may have low levels of genetic diversity; This is a specific type of Genetic Drift

Hybridization

When 2 species with incomplete reproductive barriers come in contact with one another Gene flow BETWEEN species, NOT WITHIN species

Hybrid Zones

Region where members of different species with incomplete reproductive barriers meet, mix, and mate in the wild

Stages of Hybrid Zones Overtime

Reinforcement Fusion Stability

Reinforcement

1)Strengthening/Reinforcing of reproductive barriers Hybrids are less fit than their parents Gradually, fewer hybrids are formed

Fusion

1)Weakening of the Reproductive Barriers Gene flow between 2 species increased over time Two species may eventually fuse back together into 1 species.

Stability

A few hybrids consistently produced every year/season Number of hybrids isn't decreasing or increasing over time

LUCA

Last universal common ancestor

Stromatolites

Fossilized mats of cyanobacteria Represent some of the very earliest living things on the planet (possibly what LUCA was like)

Evidence for LUCA

All Living Things share "Right-handed" spiral DNA double helix Universal genetic code (A T C G codes for specific amino acids) Same order of DNA -\> RNA -\> Protein; DNA is transcribed into RNA which is then translated into Proteins All living things have ~400 genes in common

Conditions of Early Earth

Earth Formed 4.6 Billion Years Ago Atmosphere was likely Nitrogen, Methane, Hydrogen, Carbon Dioxide, and little Oxygen Water vapor condensed to form oceans UV Radiation & Lightning striking the planet as sources of energy

Miller-Urey Experiment

Replicated early earth conditions in a lab Amino acids and nucleotides were formed Created building blocks of living material from non-living, inorganic material

First Genetic Material

RNA

Why was RNA likely the first genetic material?

It can replicate, transfer information, AND act as enzymes (it's more diverse than DNA)

RNA world hypothesis

Hypothesis suggests a self replicating RNA formed and developed into DNA/proteins

Locations of Origin of Life on Earth

Near volcanoes (due to heat) In clay/muddy pools (acts as a substrate) Deep sea hydrothermal vents Seeded by a meteorite

Extinction

Where there are no more individuals of a species alive

Why is Extinction normal in evolutionary time?

99% of all species that have ever lived are extinct Background extinction rate (\# of species that go extinct on average): ~1 per 1 million every year

Causes of Extinction

A lot of different things, often a combination

Mass Extinctions

Anywhere from 30-90% of species are no longer alive after the mass extinction

List of Mass Extinctions

Ordovician Devonian Permian Triassic Cretaceous (famous for extinction of non-avian dinosaurs) Anthropocene (extinction caused by humans)

Extinction, Speciation, and Biodiversity

It takes 5-100 million years for biodiversity to recover from a mass extinction Large scale adaptive radiation occurs after mass extinctions The number of alive species depends on 2 rates: extinction and speciation rates

Behavior

What an animal does and how it does it Subject to natural selection

What is behavior affected by?

Genetic and Environmental Factors

Ethology

The study of behavior