Evolution of Biodiversity Chapter 5 Evolution of Biodiversity

Earth is home to a tremendous diversity of species Ecosystem diversity- the variety of ecosystems within a given region. Species diversity- the variety of species in a given ecosystem. Genetic diversity- the variety of genes within a given species.

Species – can interbreed and produce viable offspring

CURRENTLY: Scientists have named 2 million species Biodiversity – most commonly measured by the number of species in any give place CURRENTLY: Scientists have named 2 million species Insect group – most diverse! Insect species – 30 million Total Estimate – between 5 and 100 million

Species richness- the number of species in a given area. Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.

Species richness or eveness often declines after a human disturbance. Knowing the species richness and eveness of an ecosystem seves as a baseline for change.

Pg. 124 Do the Math

Phylogenies – branching patterns of evolutionary relationships used to organize species. Traits used to organize species: morphology; behavior, and genetic similarity.

Why is it challenging to determine the number of species on Earth? Why are estimates of species diversity valuable to environmental scientists? What is the difference between species richness and species evenness? Why are they both important?

Evolution is the mechanism underlying biodiversity Evolution- a change in the genetic composition of a population over time. Microevolution- evolution below the species level. (varieties of apples etc) Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla. Speciation – evolution of new species

Creating Genetic Diversity Genes- physical locations on chromosomes within each cell of an organism. Genotype- the complete set of genes in an individual. Two processes that create genetic diversity: Mutation- a random change in the genetic code. Recombination – when chromosomes are duplicated during reproductive cell division and a piece of one chromosome breaks off and attaches to another.

Genotypes vs Phenotypes Phenotype- the actual set of traits expressed in an individual. (color of eyes) Genotype – blueprint for complete set of traits (genes that code for eye color).

Changes in the genotype due to mutation can cause changes in phenotype. Most phenotypes are determined by both environment and genotype. Turtle/crocodile eggs… Water flea shape By being able to respond to changing conditions, organisms can improve their ability to survive and reproduce.

Dusky-headed conure parrots

Evolution by artificial and natural selection Evolution by artificial selection- when humans determine which individuals breed. Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce.

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Darwin’s theory of evolution by natural selection Individuals produce an excess of offspring. Not all offspring can survive. Individuals differ in their traits. Differences in traits can be passed on from parents to offspring. Differences in traits are associated with differences in the ability to survive and reproduce.

Evolution by Random Processes Mutation- occur randomly and can add to the genetic variation of a population. (Fig. 5.12a) Genetic drift- change in the genetic composition of a population over time as a result of random mating. (Fig. 5.12b) Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size. (cheetah) Founder effect- a change in a population descended from a small number of colonizing individuals. (island)

Let’s Review… What is evolution, and what are the 3 main ways in which it occurs? How are artificial and natural selection similar? How are they different? How does evolution lead to biodiversity?

How do we go from Microevolution to Macroevolution?

Speciation and extinction determine biodiversity Allopatric speciation- when new species are created by geographic or reproductive isolation.

Sympatric speciation- the evolution of one species into two species in the absence of geographic isolation, usually through the process of polyploidy, an increase in the number of sets of chromosomes. Naturally or through human action (breeders – crops, strawberries, bananas etc) Polypolid cannot interbreed with diploid ancestors – naturally isoated.

The pace of evolution Can take hundreds to millions of years Average is one new species every 3 million years. Fig. 5.16 – RAPID - cichlid fishes

The pace of evolution FIG 5.17 Four factors for successful adaptation: Rate of environmental change (acidic lakes) Genetic variation (high variation = more chance of new species) Population size (smaller = more likely to have new species) 4. Generation time (shorter generation time = more likely evolve)

The pace of evolution

Evolution occurs more rapidly in populations of GMOs. Bacillus thuringiensis – produces insecticide Bt – corn, Bt-cotton

Review How does geographic isolation lead to reproductive isolation? What factors influence a species chances of adapting successfully to a change in the environment? Why is the pace of human-driven evolution faster than that of natural evolutionary processes?

Evolution shapes ecological niches and determines species distributions Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance. Fundamental niche- the ideal conditions for a species.

Biotic factors can limit a niche as well: Competition Predation Disease

Niches Realized niche- the range of abiotic and biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives. Niche generalist- species that live under a wide range of conditions. Niche specialist- species that live only in specific habitats.

Generalist Specialist Spittlebug Leaf Beetle

Environmental Change and Species Distribution Evidence: Lake sediment/pollen Fig. 5.20 – red pine vs loblolly pine

Environmental Change and Species Extinctions Avg. lifespan of a species – 1-10mill years. 99% of species that once lived – EXTINCT!

Why do species go extinct? No favorable environment Polar bears May be occupied (Fig. 5.21) Too rapid of a change

The Fossil Record Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record.

The Five Global Mass Extinctions Mass extinction- when large numbers of species went extinct over a relatively short period of time. 251 mya – largest on record 65 mya - dinosaurs

The Sixth Mass Extinction Scientists feel that we are in our sixth mass extinction, occurring in the last two decades. Estimates of extinction rates vary widely, from 2 % to 25% by 2020. In contrast to previous mass extinctions, scientists agree that this one is caused by humans.

How do fundamental niches and realized niches differ? Review How do fundamental niches and realized niches differ? How does environmental change determine species distribution? When does environmental change lead to extinction? How are human activities affecting extinction rates? Why is human impact a concern at all? (why should we care?)