AP Biology - Unit 7 Natural Selection

Biodiversity

_________ is the variety of life and is the result of evolution over time

Evolution

Change in allele frequencies in a population over time

Adaptations

Inherited traits that increase an organism’s fitness

Fitness

Ability of an organism to survive and reproduce

Genetic variation

Differences in DNA among individuals in a population that allow evolution to occur

Mutation

Random change in DNA that creates new genetic variation

Effect of mutations

Most are harmful but some are beneficial (adaptive)

Microevolution

Small-scale evolution within a population (short time scale)

Macroevolution

Large-scale evolution leading to new species (long time scale)

Artificial selection

Humans select traits and control breeding

Example of artificial selection

Dogs and crops bred for desired traits

Consequence of artificial selection

Reduced genetic diversity

Natural selection

Environment selects individuals with beneficial traits

Survival of the fittest

Individuals with highest fitness reproduce more

Random processes (nonadaptive evolution)

Genetic changes not related to fitness

Gene flow

Movement of individuals (and genes) between populations

Genetic drift

Random change in allele frequencies (stronger in small populations)

Bottleneck effect

Drastic reduction in population reduces genetic diversity

Founder effect

Small group starts new population with limited genetic variation

Rate of evolution

Usually slow but faster in small populations or strong selection pressures

Gradualism

Slow

Punctuated equilibrium

Rapid bursts of evolution followed by stability

DNA

Genetic material found in all cells

Genes

Segments of DNA that code for proteins

Chromosomes

Structures that organize DNA (humans have 23 pairs)

Mutation effect on proteins

Changes DNA sequence which can alter protein shape/function

Fossils

Preserved remains of organisms that provide evidence of past life

Fossil formation

Rapid burial and mineralization of remains

Fossil record

Collection of all discovered fossils showing history of life

Relative dating

Determining age based on rock layer position (deeper = older)

Absolute dating

Determining exact age using radioactive decay

Half-life

Time it takes for half of a radioactive isotope to decay

Carbon-14 dating

Used to date relatively recent fossils (~5

Homologous structures

Similar structures due to common ancestry

Example of homologous structures

Vertebrate limbs

Analogous structures

Similar function but different evolutionary origin

Vestigial structures

Remnants of features with little/no current function

Example of vestigial structures

Whale pelvis

Homologous proteins

Similar proteins indicating common ancestry

Highly conserved proteins

Proteins nearly identical across many species

Example of conserved protein

Cytochrome C

Pax6 gene

Highly conserved gene controlling eye development

Comparative genomics

Comparing DNA sequences between species to determine relationships

Common ancestry

All life evolved from a shared ancestor

Three domains of life

Bacteria

Endosymbiotic theory

Eukaryotic cells formed when prokaryotes engulfed other cells

Mitochondria origin

Evolved from aerobic bacteria

Chloroplast origin

Evolved from photosynthetic bacteria

Hardy-Weinberg equilibrium

Allele frequencies remain constant (no evolution)

Conditions for Hardy-Weinberg

No selection

Purpose of Hardy-Weinberg

Null hypothesis to detect evolution

P + Q = 1

Allele frequency equation (dominant + recessive = 1)

P² + 2PQ + Q² = 1

Genotype frequency equation

P²

Homozygous dominant frequency

2PQ

Heterozygous frequency

Q²

Homozygous recessive frequency

Cladogram

Diagram showing relationships without time

Phylogenetic tree

Diagram showing relationships with time

Node

Represents a common ancestor

Branch

Represents evolutionary lineage

Divergent evolution

Species evolve differently from a common ancestor

Convergent evolution

Unrelated species evolve similar traits

Parallel evolution

Related species evolve similar traits independently

Co-evolution

Two species evolve in response to each other