Evolution of Biodiversity Chapter 5 Evolution of Biodiversity

The Dung of the Devil 1918-1920  Spanish flu- unprecedented flu outbreak Mortality estimates vary 20 mil – 100 mil worldwide In China – found the roots of a particular plant with beneficial properties to fight the flu (Ferula assafoetida ) H1N1 virus caused Spanish flu – similar to H1N1 that caused the “swine flu” outbreak Other organisms we have extracted life-saving drugs from: Of most promising current candidates for new drugs – 70% were first discovered in plants, animals and microbes Problem? Why talk about this?

Earth is home to a tremendous diversity of species Ecosystem diversity- the variety of ecosystems within a given _______ Species diversity- the variety of species in a given ______________ Genetic diversity- the variety of genes within a given ____________ Diversity among individuals **All three scales of biodiversity contribute to the overall biodiversity of the planet**

How many species live on Earth? Species – a group of organisms that is distinct from other groups in terms of size, shape, behavior or biogeochemical properties Must be able to … Problems estimating population size To date: approximately 2 millions species named Current estimates for total number of species 5-100 million

Definitions 2 measure to help determine diversity: Species richness- Species evenness- Must evaluate together

Determining Evolutionary Relationships Among Species Phylogenies – branching patterns of evolutionary relationships Can be described in a diagram  phylogenetic tree

Evolution is the Mechanism Underlying Biodiversity Evolution- a change in the genetic composition of a population over time Occurs at multiple levels (remember KPCOFGS): Microevolution Macroevolution Speciation Depends on genetic diversity

Creating Genetic Diversity Genes- physical locations on chromosomes within each cell of an organism Genotype- the complete set of genes in an individual 2 processes that create genetic diversity (occur over an organism’s lifetime): Mutation- Caused by: Must occur where in order to be passed on? Recombination – when chromosomes are duplicated during meiosis

Creating Genetic Diversity Phenotype- the actual set of traits expressed in an individual Includes: anatomy, physiology and behavior Effected by both:

Evolution occurs by… Artificial selection Natural selection Random processes

Evolution by Artificial Selection Evolution by artificial selection- when humans determine which individuals breed Selecting for desired traits Examples: Unintended consequences: Resistance!!

Evolution by Natural Selection Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce Adaptations –

Darwin’s theory of evolution by natural selection Individuals produce an excess of offspring. Not all offspring can survive. 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 Random processes (does not relate to a change in fitness): Mutation- occur randomly and can add to the genetic variation of a population Genetic drift- Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size Founder effect-

Speciation and extinction determine biodiversity Moving from microevolution to macroevolution: Allopatric speciation- Ways to create a new species: Geographic isolation – due to founder effect Reproductive isolation –can no longer interbreed and produce viable offspring Example: Darwin’s Finches More common method of speciation

Speciation and extinction determine biodiversity 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 Result of _______________________ vv– increase in the number of chromosomes Polyploid organisms cannot interbreed with diploid ancestors

The pace of evolution Long time  hundreds to millions of years Influence of 4 factors on successful adaptation: a – rate of environmental change b – genetic variation c – population size d – generation time

The pace of evolution Evolution by artificial selection is faster than by natural selection Evolution occurs more rapidly in populations of GMOs Genetic engineering –

Evolution shapes ecological niches and determines species distributions Range of tolerance- the limit to the abiotic conditions organisms can tolerate However, all species have an optimal environment Fundamental niche- the ideal conditions for a species

Niches Realized niche- the range of abiotic and biotic conditions under which a species lives Determines the species distribution Niche generalist- species that live under a wide range of conditions Niche specialist-

Environmental change and species distributions Species vary in ability to adapt Move physically

Predicting future species distributions We try to predict how distributions might change as a result of future changes in environmental conditions

Environmental changes and species extinction Species that cannot adapt to changes go extinct 99% of all species that have ever lived on Earth are now extinct Why do species go extinct?

The Fossil Record So how do we know about evolution of life? Fossils- Oldest fossils are found further down in sediment  can estimate age of fossils Most organisms do not become fossils

The Five Global Mass Extinctions Mass extinction- when large numbers of species went extinct over a relatively short period of time 5 global mass extinctions: 251 million ya – 90% of marine species and 70% of land vertebrates went extinct 65 million ya – ½ of Earth’s species (including dinosaurs) went extinct

The Sixth Mass Extinction Scientists feel that we are in our sixth mass extinction, occurring in the last two decades In contrast to previous mass extinctions, scientists agree that this one is caused by ______________________________ Including: habitat destruction, overharvesting, introductions of invasive species, climate change, and emerging diseases