I. I.Population Ecology D. D.Population Dynamics 3. 3.Life History Strategies Finite amount of energy to allocate among growth, reproduction, metabolism Some species maximize reproduction; others maximize survival a. a.r-selection Opportunistic species in variable environments Population usually much higher or much lower than carrying capacity Many weed/pest species b. b.K-selection Usually in stable environments Population usually at/near carrying capacity Many endangered species Why?
I. I.Population Ecology D. D.Population Dynamics 4. 4.Factors Affecting Population Growth/Size a. a.Density-Independent Factors Catastrophic events Ex: Floods, fires, drought, storms, extreme weather Some aggregated organisms and social animals can enhance resistance to density-independent factors Ex: Emperor penguins, clustered plants/animals b. b.Density-Dependent Factors Effects increase as population size increases 1. 1.Competition – Limit = resources (food, water, etc.) Territoriality – Limit = space availability 1. 1.Health – Includes disease 2. 2.Predation – Selective by predator(s) 3. 3.Wastes – Toxic at higher concentrations 4. 4.Other Factors – Ex: Aggression at higher densities
I. I.Population Ecology D. D.Population Dynamics 5. 5.Population Stability Stability usually related to lifespan, reproductive rate a. a.Environmental factors Resource availability Recruitment b. b.Immigration Metapopulations may be more stable than isolated populations
I. I.Population Ecology D. D.Population Dynamics 5. 5.Population Stability Stability usually related to lifespan, reproductive rate a. a.Environmental factors Resource availability Recruitment b. b.Immigration Metapopulations may be more stable than isolated populations c. c.Combined factors Resources, predation, etc.
II. II.Community Ecology Focus on interspecific interactions May be direct or indirect A. A.Competition Two or more species competing for scarce resource Ex: Two plant species competing for water May be detrimental to one or both species 1. 1.Competitive exclusion No two species can use same set of resources in same area at same time Competitively dominant species tend to force extinction of competitively inferior species
II. II.Community Ecology A. A.Competition 2. 2.Ecological niche Species’ ecological role in a community Includes use of abiotic and biotic resources Niche occupied by a species may be narrower than range of conditions tolerated by species Fundamental niche vs. realized niche
II. II.Community Ecology A. A.Competition 4. 4.Character displacement Resource partitioning may lead to directional selection on one or both species Directional selection may lead to divergence in traits
II. II.Community Ecology B. B.Predation Involves consumption of prey by predator Predator usually has adaptations to facilitate capture of prey Natural selection acts on both predator and prey Coevolution 1. 1.Strategies a. a.Pursuit predation Predators chase prey to capture them Predator usually faster, stronger, &/or more agile than prey Some species hunt in groups b. b.Ambush predation Predators lie in wait for prey Predators usually camouflaged or concealed May involve lures c. c.Aggressive mimicry Ex: Bolas spider mimics odor of female moths to attract male moths
II. II.Community Ecology C. C.Herbivory Consumption of plants by animals Most herbivores are small Ex: Insects, snails/slugs Herbivores adapted to consume plants Some plants have anti-herbivore defenses Physical – Ex: Thorns, spines Chemical – Ex: Nicotine in tobacco, pyrethrins in chrysanthemums Coevolution has affected herbivore evolution Ex: Monarch butterfly caterpillars can eat milkweed Toxic to most herbivores Nearly exclusive access to food source Can sequester noxious compounds for defense
II. II.Community Ecology D. D.Parasitism Parasite benefits at expense of host Host harmed in process Ex: Tapeworm absorbs nutrients from host digestive system Endoparasites – Live within body of host Ectoparasites – Live outside body of host Parasitoids – Lay eggs on/in host; larvae feed on host, eventually killing host Many parasites have complex life cycles Fig. 33.12