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 biodiversity I. Evolution (an ongoing process) A. evolution = genetic change in 1. may be caused by random changes 2. may be caused by natural selection B. natural selection = process by which traits that enhance survival & reproduction C. Understanding evolution is vital 1. alters genetic makeup of a popn ; imp. for understanding 2. organisms adapt to environ. & change over time. D. Natural selection as mechanism for evolution 1. 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 creation 2. sympatric speciation = species form from How can this occur? -feed in diff. areas, mate in diff. seasons -hybridization between 2 species -Mutations Speciation results in diverse life forms 3. generates complex patterns of diversity above the species level -phylogenetic trees (cladograms) = represents the history of II. Extinction A. 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 extinctions C. Extinction events 1. background extinction rate = 2. mass extinction events = 5 events in Earth’s history that 3. humans are causing the sixth mass extinction event: HIPPO III. 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 ecology A. 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 same B. 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 found Population chs. Population changes affect communities V. Challenges to protecting biodiversity Preserving biodiversity B. Natural parks & protected areas help preserve biodiversity -often, underfunded -ecotourism brings jobs & money to developing
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