Bio 163 patterns of evolution and genes lmk 2013

Patterns and Processes of Evolution

Macroevolutionary Patterns Large-scale (more than a single species) Occurs over long periods of time

Microevolution Small-scale (within a single species) Forms variations in populations

1

Speciation – Isolating MechanismSpecies – group of organisms that interbreed to

produce fertile offspring under normal conditions –

share a common gene poolSpeciation – formation of a new species

Requires reproductive isolation – organisms do not interbreed; gene pools become separateBehavioralGeographicTemporal

2

Patterns of Extinction

Background Extinction – “business as usual” extinction – slow and steady

Mass Extinction – many species become extinct over a short period of timeCauses:AsteroidVolcanic eruptionsMoving continentsChanging sea levels

3

Rates of Evolution

Gradualism – change in species is slow and steady

Punctuated Equilibrium – long periods of stability followed by short periods of rapid change

4

Patterns of Macroevolution:

Adaptive RadiationA single species evolves into many speciesOften occurs when a niche opens up

5

Organisms come to resemble one another but evolved differently

Source of analogous structures!

Examples: Dolphins and sharks Marsupials and

mammals

Patterns of Macroevolution:

Convergent Evolution

6

Coevolution

Organisms with close ecological relationships evolve togetherPollinators and flowers

7

The Role of Genes in Evolution

In terms of genetics, evolution is the change in the frequency of alleles in a population’s gene pool

Natural selection leads to that change

8

Genetic DriftRandom change in allele frequency –

changes in the gene pool of a small population due to chance

Types of Genetic Drift: Bottleneck Effect – change in allele

frequency following dramatic reduction in population size

9

Genetic Drift Founder Effect – small group colonizes a

new habitat

10

Molecular Evolution

Molecular Clocks – use mutation rates in DNA to estimate time two species have been evolving independently

11

Molecular Evolution: Hox Genes

12

Genes which control an organism’s basic body plan Anterior/posterior ends Limbs, wings

small sequence changes during embryological development can cause large changes in adults