 Why is there only two wolves at the top of the pyramid and 6 rabbits in the next level down? 2 Wolves 6 Rabbits 2000 Blades of Grass

A large percentage of the energy is lost between trophic levels. This is as a result of the following: Some of the organism cannot be eaten, e.g. bones, fur, etc. Once eaten, some of the organism cannot be digested. Energy is lost in excretory materials, such as urine. Energy is lost in the form of heat from respiration and body heat.

 What is “biodiversity”?  How did the Earth get so diverse?  Why are there so many different species of plants and animal?

Charles Darwin The Origin of Species by Means of Natural Selection (1859)

 Inherited traits favorable to survival in a given environment would tend to be preserved and unfavorable ones would be eliminated.  Adaptations: Evolutionary modifications that improves the chances of survival and reproductive success of the population in a given environment.

Those individuals with a combination of genetic traits better suited to environmental conditions are most likely to survive and reproduce. Four components of Natural Selection: 1. overproduction 2. variation 3. limits on population growth, or a struggle for existence 4. differential reproductive success

Gene pool: The sum total of all genes possessed by the individuals of the population of a species. Microevolution: small genetic changes that occur in a species gene pool over time. Example: Camouflage coloration in the peppered moth

First an environmental change occurred: Soot caused a change in the background color of the tree trunks. Then the environmental change led to a change in selective forces: Predators were able to find and eat the moths with the coloration that no longer blended in with the background. SOOOOOOO….

1. There were two colors forms (Variability in the genes) 2. Color form was genetically based ( heritability of the genes) 3. There was greater survival and reproduction by one of the color forms ( differential reproduction) Microevolution took place!!!!

 Environmental conditions do not create favorable heritable characteristics… inherited genetic variations  Instead, natural selection favors some individuals over others by acting on inherited genetic variations (alleles) already present in the gene pool of a population.

 Natural selection changes characteristics through:  Directional selection = drives a feature in one direction  Stabilizing selection = favors intermediate traits  Preserving the status quo  Disruptive selection = traits diverge in two or more directions

 Artificial Selection = the process of selection conducted under human direction  Producing the great variety of dog breeds and food crops

Tropical Rainforest and coral reefs have extremely high species richness.  Isolated islands and mountain tops have low species richness Created by Geographical Isolation

 The number of species in existence at any time is equal to the number added through speciation minus the number removed by extinction. kim-preshoff

1. Abundance of ecological niches Greatest at the margins of adjacent communities ecotone – a transitional zone where two or more communities meet edge effect- the change in species composition produced at ecotones 2. Inverse relationship to the geographical isolation of a community. 3. Reduced when one or more species is dominant in a community (competition) 4. Inversely related to the stress on a habitat 5. Geological history – (climate changes)

Ecosystems with greater species richness are better able to supply ecosystem services – environmental benefits, such as clean air, clean water, and fertile soil. Community stability – the ability of a community to withstand environmental disturbances Example: monocultures and pest vs. blight on a specific trees in a forest of other species

Long term large-scale evolutionary changes among groups of a species. New species are formed from ancestral species and other species are lost through extinctions. Phylogenetic tree (cladogram)

Macroevolutionary patterns include: 1.Genetic persistence – the inheritance of DNA molecules from the origin of the first cells through all subsequent lines of descent ( basis of the unity of life) 2.Genetic divergence – long-term changes in lineages of species (basis of the diversity of life) 3.Genetic losses – the steady loss through background extinction or mass extinctions (abrupt, catastrophic loss of lineages)

MUTATION: CHANGES IN DNA OF A CELL GENETIC DRIFT: CHANGES IN THE GENETIC COMPOSITION OF A POPULATION BY CHANCE.

Movement of genes between populations. This can lead to changes in the genetic composition of local populations. Gene Flow:

 Allopatric speciation (geographical isolation): species formation due to physical separation of populations  The main mode of speciation  Populations can be separated by glaciers, rivers, mountains  Each population gets its own set of mutations

 Sympatric speciation (reproductive isolation): species form from populations that become reproductively isolated within the same area  Feed in different areas  Mate in different seasons  Hybridization between two species  Mutations

 Divergent evolution: Related species in different environments  Experience different pressures causing the allele frequency to change  Evolve different traits  Convergent evolution = unrelated species may evolve similar traits  Because they live in similar environments

Organisms evolve together

 How do major groups diverge over time?  Phylogenetic trees (cladograms) = show relationships among species, groups, genes, etc.  Scientists can trace how certain traits evolved

Previous 5 Mass Extinctions: Are we in the 6 th Mass Extinction???

In mass extinctions, large numbers of species become extinct each year for tens of thousands to millions of years. The five great mass extinctions have occurred during the past 500 million years and have been million years apart. There have also been shorter mass extinctions (loss of 15-24% of all species) in between. A period of mass extinction is often regarded as having a loss of 25-70% of all species. The extinction of the dinosaurs is an example of mass extinction.

All mass extinctions have been followed by periods of recovery, known as adaptive radiations. After almost every mass extinction, numerous new species have evolved (speciation) to fill new or vacated ecological niches in the changed environment. The extinction of dinosaurs, for example, was followed by an explosive rise of mammals. Fossil records suggest about 10 million years or more are required for adaptive radiations to rebuild biological diversity after a mass extinction.

Background extinction refers to the extinction that occurs naturally in the evolution process % of species become extinct naturally according to fossil records. During the ecological process, the natural extinction occurs following the evolution of the species. If a species cannot succeed in adapting to its surroundings it eventually becomes extinct.

 1. gradual changes in temperature  2. predator-prey relationships  3. tectonic plate movements. It is estimated that the average species stays around for 4 -22million years before it becomes extinct and that 99.9 of all the species that have ever existed are now extinct.

 Humans profoundly affect rates of extinction  Biodiversity loss affects people directly  Food, fiber, medicine, ecosystem services