AP Bio Unit 7 (2)

Descent with modification

Over time species accumulate differences from their ancestors

What is descent with modification the result of?

the change in genetic composition of a population over time

What is the reason for the large amount of diversity we see today?

Descent with modification

Adaptations

Inherited characteristics that enhances an organisms ability to survive and reproduce

Natural Selection

Individuals with certain inherited traits tend to survive and reproduce better than those without those traits

Differential survival

Individuals with heritable, advantageous traits are more likely to survive and reproduce than others

What individuals are more likely to survive?

Individuals with more favorable phenotypes

Evolutionary fitness

Measure of an organism's ability to survive and reproduce

Common ancestor

Many organisms share similar traits because they descended from a common ancestor

What happens when the environment surrounding an individual changes?

The traits needed to survive may change

What creates genetic variation?

Due to random mutations, crossing over in meiosis, sexual reproduction, and gene flow

What creates a competition for resources?

Organisms within a population create more offspring and not all of them will survive?

What individuals are more likely to survive and reproduce?

Those with adaptations that increase evolutionary fitness

What does natural selection act on?

Individuals

What does evolution act on?

populations

Structural adaptations

Physical differences in body or biological structure (Ex. camouflage)

Behavioral adaptations

Difference in behavior patterns (Ex. hibernation)

Physiological adaptations

Variation in physiological differences (Ex. Metabolism)

Selective pressures

An external factor that impacts an organism's ability to survive and reproduce

Density-dependent factors

Have a greater impact based on the population size

Density-independent factors

Same impact regardless of the population size

Examples of selective pressures

Resource availability

Environmental conditions

Biological factors

Heterozygote advantage

Occurs when heterozygotes hvae higher fitness than homozygotes

Sexual selection

If an organism is more attractive to another organism, that organism will be more likely to pass down their traits

Sexual dimorphism

Males and females who differ in size and other traits

Heritability

The favorable trait, or adaptation, must be genetic and capable of being inherited by the next generation

adaptive evolution

an increase in the frequency of alleles that improve fitness

Sources of heritable variation

Crossing over, independent assortment, random fertilization, and mutations

Directional selection

occurs when conditions favor individuals at one end of the phenotypic range

Disruptive selection

occurs when conditions favor individuals at both extremes of the phenotypic range

Stabilizing selection

occurs when conditions favor intermediate variants and act against extreme phenotypes

Convergent evolution

the independent evolution of similar features in species of different lineages

How is convergent evolution NOT inherited?

Through common ancestry

Divergent evolution

the process where related species evolve distinct, dissimilar traits from a common ancestor,

When can evolution occur faster?

When a species produces new generations in a quicker period of time

What does natural selection do?

Edits traits that are already present

What does natural selection depend on?

The environment

How does natural selection respond to invasive species?

Aspects of an individual will change in order to adapt to the new environment with the invasive species

How does natural selection develop a resistance to drugs?

Bacteria that contain the antibiotic resistant genes are more likely to reproduce as they are better fit for their environment

Fossils

Preserved remains or traces left behind by any organism from the past

Fossil Record

All the fossils that have been found (not complete)

Transitional features

Characteristics that are intermediate between an ancestral group and its predicted descendants

What do transitional features show?

A mix of traits that blend older and younger groups

Relative dating

Determining the age of the fossil based on the rock layer (strata)

Does relative dating determine a fossils exact age?

No

Radiometric dating

Determines the numerical age of a fossil involving the decay of radioactive isotopes

Radioactive isotope

Used to infer the relationship between different fossils

Half-life

The rate of decay

Homology

A similarity shared between species that is a result of common ancestry

Homologous structure

Structures that are anatomical similar but have different functions

Analogous structure

Structures that share a common function but not structure

Vestigal structures

a structure in a present day organism that no longer serves its natural purpose

What does the universal genetic code suggest regarding evolution?

That all organisms came from a common ancestor

Highly conserved genes

found in almost every living organism and change very little over time

What does a larger difference in nucleotide sequences mean in terms of ancestry?

More time has passed since the organisms shared a common ancestor

Biogeography

The study of the geographic distribution of species

Continental drift

The slow movement of Earth's continents overtime

Pangaea

When all of earth's continents were united together under one continent

Endemic

Organisms that are found in only one place and no where else in the world

Morphologies

The outward appearance, internal structure, and form of organisms

Systematics

The study of the classification and evolutionary relationships among different species

Taxonomy

The discipline of using similarities and differences in order to name and classify different species

Taxonomic levels

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Binomial nomenclature

The two part Latin naming system that biologists use to classify organisms

What does the branching patterns represent in phylogenetic trees and cladograms?

the evolutionary lineage

What does the node/branch point represent in phylogenetic trees and cladograms?

a common ancestor species that the organisms at the end of the branch share

Root diagram

The initial branch point (the root) represents the most recent common ancestor of all taxa in the tree

Sister taxa

A group of organisms that share an immediate common ancestor

Outgroup

Represents the lineage that is least closely related to the other groups

What do phylogenetic trees and cladograms infer?

the two lineages shared a common ancestor in evolutionary history

What does it mean when organisms share more homologies?

They are closer related

Molecular clock

When some genes accumulate mutations at a relatively constant rate (about 1 bp change/time)

Typically when structures are more complex, what does that mean?

the more likely the structures are actually homologous and it's less likely they developed independently

Cladogram

Focus on shared characteristics DO NOT show change over time

Phylogenetic trees

Shows specific changes over time using fossil and molecular data

Shared derived character (synapomorphy)

A trait that evolved in a recent common ancestor and is shared by its immediate descendants, but is absent in more distant ancestor

Maximum parsimony

First consider the simplest explanation fo differences in species and construct trees with fewest evolutionary or genetic changes

Hardy-Weinberg equation

Used to determine if a population is evolving by comparing observed genotype frequencies against expected frequencies when no evolution occurs

5 principles of Hardy Weinberg

There must be no mutations

Random mating

No natural selection is occurring

The population size is extremely large

What does it mean when a hardy-weinberg principle is violated?

evolution is actively occurring among this population

What hardy Weinberg equation is used for phenotypes?

p + q = 1

What Hardy Weinberg equation is used for genotypes?

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

What does p represent in hardy weinberg?

the dominant allele frequency

What does q represent in hardy weinberg?

the recessive allele frequency

What makes evolution possible?

Genetic variation

Microevolution

Change in allele frequencies in a population over generations.

Allele frequency

How frequent certain alleles for a gene are found within a population

What does natural selection change within a population?

Allele frequencies

Genetic variation

Differences in the composition of sequences of genes

How can organisms appear very similar but every very different nucleotide sequences?

Variation in intron sequences and silent mutations that code for the same amino acid

What populations are more resistant to environmental changes?

Those with greater genetic diversity

What does lower genetic variation result in?

Extinction of a species

Gene pool

All copies of every type of allele for a gene within a population

Fixed alleles

When all members of a population are homozygous for a specific allele

Natural selection

Survival and reproductive successes are driven by environmental pressures

Adaptive evolution

Traits that increase survival and reproduction tend to increase frequency within a population overtime

Genetic Drift

Random events that cause allele frequencies within a population to change

What population does genetic drift have a greater affect on?

Smaller populations

Founder effect

Few individuals become isolated from a larger population creating a new population that may have different allele frequencies

What does the founder effect result in?

A loss of genetic variation and can lead to the evolution of distinct species