Ch5: Evolution, Biodiversity, & Population Ecology• Evolution gives rise to Earth’s enormous biodiversity• Humans are causing a massive extinction of species• Life forms belong to increasingly large organizational units• Populations are typically dynamic/changing• Conservation biology is concerned with protecting Earth’s biodiversityI. Evolution (an ongoing process)A. evolution = genetic change in 1. may be caused by random changes2. may be caused by natural selectionB. natural selection = process by which traits that enhance survival & reproduction C. Understanding evolution is vital1. alters genetic makeup of a popn ; imp. for understanding 2. organisms adapt to environ. & change over time.D. Natural selection as mechanism for evolution1. Charles Darwin & Alfred Russell Wallace (1858) 2. major concepts (Table 5.1, page 114):Organisms struggle for existence Individuals of a species vary in their Some individ. are better suited to 3. adaptive trait (adaptation) = a trait that promotes 4. acts on natural variation due to:- mutations = changes in - sexual reproduction- genetic drift = E. artificial selection (selective breeding) = process of selection conducted under F. Generates biodiversity• biological diversity = an area’s sum total of - diversity of • species = a popn or group of popns whose members share • population = a group of individ. of a species that G. speciation produces new types of organisms (species)1. allopatric speciation = species ENV 2100 Environmental Science, Dr. L. Kelly- by way of - the main mode of species creation2. sympatric speciation = species form fromHow can this occur?- feed in diff. areas, mate in diff. seasons- hybridization between 2 species- MutationsSpeciation results in diverse life forms3. generates complex patterns of diversity above the species level- phylogenetic trees (cladograms) = represents the history of II. ExtinctionA. extinction = loss of a Extinction is a natural process• Extinction is irreversible: • Humans profoundly affect B. endemic species = exists only in a certain, Earth has had several mass extinctionsC. Extinction events1. background extinction rate =2. mass extinction events = 5 events in Earth’s history that3. humans are causing the sixth mass extinction event: HIPPOIII. Ecology is studied at several levels• Ecology & evolution are tightly intertwined• Several levels of organization:• biosphere = the total living forms on)• ecosystem = communities & the • community = interacting species that Levels of ecological organization• population ecology = investigates quantitative dynamics of • community ecology = focuses on interactions among • ecosystem ecology = studies living & III. Organismal ecologyA. habitat = environ. (place) in which- includes living/nonliving elements- scale-dependent B. habitat selection = process by which availability & quality of habitat are C. niche = an organism’s use of D. specialists = spp. with E. generalists = spp. with broad IV. Population chs.A. popn size = total number of - numbers can increase, decrease, cycle or remain the sameB. popn density = number of 1. high densities --- 2. low densities – C. popn distribution (range) = D. popn dispersion = spacing individ. with 1. random – 2. uniform –3. clumped – E. sex ratio = F. age structure =G. Birth and death rates 1. crude birth/death rates = 2. survivorship curves = - Type I: more deaths at - Type II: equal number of deaths at - Type III: more deaths at H. Movement of individ.1. immigration = 2. emigration = I. exponential popn growth- bigger the popn, faster it grows-J. Most popns are constrained by limiting factors =K. carrying capacity = - an S-shaped logistic growth curve- limiting factors slow and L. Factors affecting popns 1. density-dependent factors = 2. density-independent factors = Perfect logistic curves aren’t often foundPopulation chs.Population changes affect communitiesV. Challenges to protecting biodiversityPreserving biodiversityB. Natural parks & protected areas help preserve biodiversity- often, underfunded- ecotourism brings jobs & money to developing