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

Measuring Species Species evenness 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 – 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 Mutation – random change in a gene during replication Recombination 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 Genotype – the blueprint Phenotype 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 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 fitnessadaptation N.S. favors combination of traits that improves fitness; process is called adaptation

Random Processes Changes are not related to differences in fitness Mutation Mutation – if not lethal, can add to the genetic variation of a population Genetic drift Genetic drift – change in the genetic composition of a population as a result of random mating (impt in smaller populations)

Random Processes Bottleneck effect Bottleneck effect – a drastic reduction in the size of a population; genetic composition also reduced Founder effect Founder effect – change in a population descended from a small number of colonizing individuals

SPECIATION

Allopatric v. Sympatric Speciation Allotropic speciation Allotropic speciation is the process that requires geographic isolation – Similar to the founder effect Sympatric speciation 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 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 Range of Tolerance – limits to the abiotic conditions they can tolerate fundamental niche The suite of ideal conditions is termed the fundamental niche of the species Biotic factors also exist realized niche The range of abiotic and biotic factors under which a species lives is the realized niche

Ecological Niches Niche generalists Niche generalists – able to live in a variety of habitats or feed on a variety of species Niche specialists 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 The Fossil Record – remains of organisms preserved in rock 5 major extinctions 5 major extinctions have occurred in the past 500 million years – Largest: – Largest: Permian extinction (90% of marine life) – Most famous: – Most famous: Cretaceous (end of the dinos) 6 th mass extinction: 6 th mass extinction: going on now? Some estimates: up to 25% by 2020