A Diverse Planet

Evolution & Biodiversity

Home of the Diverse

• Ecosystem Diversity–Different ecosystems within a region

• Species Diversity–Variety of species within an ecosystem

• Genetic Diversity–Variety of genes within a species

How Many Species?

• The number of species in any given place is the most common measure of biodiversity

• Named: 2 million species• Estimate: 5 – 100 million

Measuring Species

• Species richness: number of species in a given area (pond, tree canopy, grassland)–Used to give an approximate sense biodiversity

Measuring Species

• Species evenness: tells whether an ecosystem is dominated by one species or if there is ‘even’ abundance of all species–High evenness: if all species are represented

by similar numbers

Evolutionary Relationships

• Species organized into categories that indicate how closely related they are

• Phylogenies – branching patterns of evolutionary relationships

• Relatedness determined by similarity of traits

Creating Genetic Diversity

• Evolution – the change in the genetic composition of a population over time

• Microevolution – occurs below the species level (apple, potato varieties)

• Macroevolution – gives rise to new species, genera, etc.

Creating Genetic Diversity

• Mutation – random change in a gene during replication

• Recombination – during reproductive cell division, a piece of one chromosome breaks off and attaches to another; can produce new traits (immune system)

Creating Genetic Diversity

• Genotype – the blueprint• Phenotype – the set of traits expressed• Phenotype determined by genotype, but is

influenced by environment• Example –turtle, crocodile egg temps can

determine gender

Artificial Selection

• Humans determine which individuals breed when a preconceived set of traits desired

Natural Selection

• The environment determines which individuals survive and reproduce

• Proposed by C. Darwin• Differences in traits are associated with

differences in the ability to survive and reproduce

• N.S. favors combination of traits that improves fitness; process is called adaptation

Random Processes

• Changes are not related to differences in fitness• Mutation – if not lethal, can add to the genetic

variation of a population• Genetic drift – change in the genetic composition

of a population as a result of random mating (impt in smaller populations)

Random Processes

• Bottleneck effect – a drastic reduction in the size of a population; genetic composition also reduced

• Founder effect – change in a population descended from a small number of colonizing individuals

SPECIATION

Allopatric v. Sympatric Speciation

• Allotropic speciation is the process that requires geographic isolation– Similar to the founder effect

• Sympatric speciation is evolution of one species into two species in the absence of geographic isolation– Can happen through polyploidy, or– exploiting a new niche may automatically reduce

gene flow

Pace of Evolution

• Average global rate is 1 new species every 3 million years

• It all depends on successful adaptation:–Rate of environmental change–Genetic variation–Population size–Generation time

Ecological Niches

• Range of Tolerance – limits to the abiotic conditions they can tolerate

• The suite of ideal conditions is termed the fundamental niche of the species

• Biotic factors also exist• The range of abiotic and biotic factors under

which a species lives is the realized niche

Ecological Niches

• Niche generalists – able to live in a variety of habitats or feed on a variety of species

• Niche specialists – able to live in a specific habitat or feed on a small group of species

Environmental Change & Species Distribution

Pine

Spruce

Birch

Prairie

Environmental Change & Species Extinction

• The Fossil Record – remains of organisms preserved in rock

• 5 major extinctions have occurred in the past 500 million years– Largest: Permian extinction (90% of marine

life)–Most famous: Cretaceous (end of the dinos)

• 6th mass extinction: going on now? Some estimates: up to 25% by 2020