APESUnit IV: Evolution and Biodiversity

Chapter 5

▪ Evolution: Change in genetic composition of a population over time

▪ population: all individuals of the same species occupying the same area.

▪ gene: unit of heritable information -usually associated (at the molecular level) with a specific region located on the chromosome.

▪ allele: - one of two or more slightly different forms, or "variants" of a given gene.

▪ genotype: a selection of the genes that make up an individual.

▪ phenotype: the consequence(s) of all the allelic interactions that give rise to a visibly   determinable "type".

Genetics 101

▪ gene pool: all the genotypes within a population.

▪ Mutation: mistake in copying of genetic code; if mutation in sex cells it is inherited.

▪ Recombination: during cell division part of one chromosome breaks off and attaches to another, which leads to new gene combinations and thus genetic diversity

▪ Evolution by Artificial Selection: Breeding dogs, horses, pea plants

▪ Unintended consequence of agricultural breeding is pesticide/herbicide resistance

I.Understanding Biodiversity

▪ HHMI: 2014 Lectures 2 and 3

▪ Biodiversity: variety of earth’s species, or varying life forms, the genes they contain, the ecosystems they live in and the ecosystem processes of energy flow and nutrient cycling that sustain life.

▪ Ecosystem Diversity

▪ Species Diversity

▪ Population Diversity

▪ Genetic Diversity

II. Human Impacts on Biodiversity

Human Impact on Biodiversity

Underlying Causes: population growth, poverty, undervaluing natural capital

Direct Causes: HIPPCO

H=Habitat Destruction, degradation and fragmentation

I: Invasive Species

P=Population growth and increase resource use

P=Pollution

C: Climate Change

O: Overexploitation

▪ Population

▪ Land Transformation

▪ Climate Change

▪ Invasive Species

▪ Diseases

▪ The role of Protected Areas

▪ Synergistic Effects

Invasive / Alien/Non-Native Species

▪ Native Species: live in their historic range-where they have lived for thousands-millions of years

▪ Alien: Live outside historic range

▪ Some species moved accidentally , some intentionally

▪ Asian Carp

http://www.cbsnews.com/video/watch/?id=5869154n

Kudzu

Zebra Mussels▪ feed by drawing water and filtering out most of the

suspended microscopic plants, animals and debris for food.

▪ can lead to increased water clarity and a depleted food supply for other aquatic organisms, including fish.

▪ The higher light penetration fosters growth of rooted aquatic plants which, although creating more habitat for small fish, may inhibit the larger, predatory fish from finding their food.

▪ Zebra mussel infestations may also promote the growth of blue-green algae, since they avoid consuming this type of algae but not others.

▪ Zebra mussels attach to the shells of native mussels in great masses, effectively smothering them

▪ http://www.nwf.org/What-We-Do/Protect-Wildlife/Invasive-Species/Ballast-Water.aspx

Population, Pollution and Climate Change

▪ Pollution: DDT

▪ Population: Bald Eagle: saved eagle but shortage of fish mean they eat baby cormorant chicks

▪ Climate Change: Cannot adapt fast enough; Polar Bearhttps://www.youtube.com/watch?v=lPgZfhnCAdI

Overexploitation: Hunting, Fishing, Illegally killing, capturing and selling wild species

III. Measuring Biodiversity

▪ Diversity and Abundance▪ Species Richness:

Number of different species▪ Species Evenness:

abundance / proportion of individuals within the species. Are all species represented by similar numbers of individuals?

III. Measuring Biodiversity

▪ Genetic Diversity and adaptation:

▪ Habitat Fragmentation:

▪ Habitat Islands:

▪ Habitat Corridors:

▪ Island Biogeography: a field within biogeography that examines the factors that affect the species richness of isolated natural communities

▪ Population Bottleneck:

▪ Pika Study:

▪ Species Richness Influenced by many factors▪ Latitude: richness declines as we move from

equator toward North or South Pole.▪ Time: Longer a habitat exists, the more

colonization and speciation▪ Theory of Island Biogeography: Influence of

SIZE of habitat an d DISTANCE

▪ Conservation: Should we establish several small reserves or a single large reserve?

IV. Evolution by Natural Selection

▪ Biological Evolution: the process whereby earth’s life changes over time through changes in genetic characteristics of populations. All species descended from earlier, ancestral species.

▪ Proposed by Charles Darwin-On the Origin of Species by Means of Natural Selection. Change in populations (not individuals) genetic makeup over successive generations. Major driving force of adaptation

Darwin’s Theory▪ Individuals produce an excess of offspring▪ Not all offspring can survive▪ Individual differ in their traits (Genetic Variability )▪ Differences in traits can be passed from parent –

offspring (differential reproduction)▪ Natural Selection: environmental conditions favor

some individuals over others

▪ Fitness: Ability to survive and reproduce

▪ Adaptation/Adaptive Traits: any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population under prevailing environmental conditions.

▪ Differential reproduction: individuals with the trait are able to survive and reproduce at a higher rate than other individuals in the population

▪ Natural Selection at work: Genetic Resistance=ability of one or more organisms in a population to tolerate a chemical designed to kill it. Antibiotic Resistance/Pesticide Resistance

▪ Limitations to adaptation through natural selection▪ Change in enviro condition can lead to adaptation only

for genetic traits already present in a population’s gene pool or for traits resulting from mutations, which occur randomly

▪ Ability to adapt limited by reproductive capacity

▪ Natural Selection acts on individuals but occurs in populations

▪ Example of Evolution by Natural Selection

Peppered Moth 

▪ Coevolution: Populations of two different species interact over a long period of time, change in gene pool of one can lead to change in gene pool of another.

▪ http://www.biotopics.co.uk/newgcse/naturalselection.html

IV. Evolution by Random Processes

▪ Genetic Drift: Change in allele frequency in a population due to random sampling. Some organisms, by chance, leave behind more offspring

▪ genetic drift with marbles

▪ Population Bottleneck: an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing; some genotypes will be lost and genetic composition of survivors will differ from original group

Founder Effect

▪ The founder effect is a special case of a population bottleneck, occurring when a small group in a population splinters off from the original population and forms a new one, taking with it only limited alleles from the original population

Summary

▪ Earth’s biodiversity is the product of evolution, a change in the genetic composition of a population over time

▪ Evolution below the species level is microevolution-variety of apples or potatoes

▪ Genetic changes that give rise to new genera, families, classes in macroevolution

▪ Extinction and speciation are what leads to biodiversity

V. Speciation and Extinction Determine Biodiversity

▪ Process of Speciaition- Two Phases

Geographic Isolation: groups from same population become physically isolated

Reproductive Isolation: When sexually reproductive organisms becomes so genetically different they cannot mate 

Pace of Evolution

▪ Hundreds to millions of years

▪ Average global rate 1 species every 3 million years.

▪ If populations cannot adapt quickly enough they go extinct

▪ To survive a rapid environmental change, a population must evolve quickly.

▪ Ecological Niche: role of an organism in ecosystem; its way of life

▪ Niche includes adaptations acquired through evolution, range of tolerance, types and amounts of resources the species uses and interactions with other organisms. Competition limits niche

▪ Limits to Adaptation-ability to adapt limited to gene pool and how fast it can reproduce.

▪ All species has an optimal environment in which it performs particularly well-a range of tolerance or limit to abiotic conditions they can tolerate.

▪ fundamental niche

▪ realized niche.

▪ A generalist species: Broad Niches able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources

▪ A specialist species: Narrow Niches can only thrive in a narrow range of environmental conditions or has a limited diet. Often prone to extinction.

▪ Most organisms do not all fit neatly into either group

IX. Environmental Changes-Physical Evolution

▪ Movement of tectonic plates has determined location of continents and ocean basins▪ Location/latitude of continents

determines climate and thus where plants and animals live▪ Movement of continents has allowed

species to move, adapt to new environments and form new species.

▪ Movement of tectonic plates has allowed species to move, adapt to new climates and form new species

▪ Volcanic Eruptions: Mt. Saint Helens: Destroy habitat and wipe out populations

▪ Earthquakes: create fissures that separate and isolate populations

▪ Climate Change and Natural Selection: Grizzly and Polar Bear

▪ Divergence: One species becomes two

▪ Convergence: The evolution of species from different taxonomic groups toward a similar form.

▪ Extinction: Species ceases to exist. They can be ecologically extinct-number are so small they cannot fulfill their role. Over 99 % of all species that have ever lived are now extinct.

▪ Endemic Species: found only in one area; are most vulnerable to extinction

▪ Background Extinction

▪ Mass Extinction

▪ The 6th mass extinction