Unit one - Ecology

1. Unit one - Ecology • Ecology literally means "study of houses," which we may interpret as • "study of living organisms in their natural surroundings." Study of ecological relationships will lead us to consideration of the characteristics of populations and of today's concerns about the quality of our environment.

2. The study of ecology-sect 31.1 • The study of interactions living things have with each other and with the environment around them • Ecology is studied at several scales of life-physiology of organisms being the smallest and biosphere constituting the largest.

3. Ecological Community • A collection of populations in a given area that potentially interact.

4. Community • Ecological dominants—those few species that are especially abundant in a given community; most are plants, but animals such as corals in a coral reef can comprise dominant species as well.

5. Community • Keystone species—those whose absence would create significant change in a community. • 1. The top predators in a community are often keystone species (e.g., sea stars of genus Pisaster, studied in Pacific Northwest by Roger Paine, who introduced the concept).Figure 31.15 • 2. Species active at other points in the food chain may comprise keystone species as well (e.g., beavers building dams).

7. community • Biodiversity refers to the complexity of species composition in a community, and these three factors contribute to its richness: (Figure 31.16) • 1. Variety of species in a community • 2. Species distribution and population size for each species • 3. Genetic variety within each population

9. Interaction between communities • 1. Populations—all members of a single species that live together in a specific geographic area (range from a small pond to several countries considered together). • 2. Communities consist of all species living in a specified geographic region (or, more restrictively, all species that potentially interact with one another in a given region.

10. 3. Ecosystems consist of communities of living things and their nonliving environment (sunlight, soil, chemical nutrients); they may be as small as a single field and as large as half a continent • 4. The biosphere is the largest scale of life; it includes the entire interactive collection of the Earth’s ecosystems.

11. Types of interaction between community members sect 31.6 • 1.Habitat—physical surroundings in which species is normally found; its “address.” • 2. Niche A.Community members occupy distinct niches within the same habitat. • —mode of living and resource acquisition for a given organism; its “occupation.” • B.Types of interaction within a community • 1. Competition for resources—usually occurs in closely related species (interspecific competition) occupying niches that overlap to some degree.

12. Competition • 1. Competition for resources—usually occurs in closely related species (interspecific competition) occupying niches that overlap to some degree. • 2. Long-standing competition for vital resources between two species with overlapping niches is unlikely. Usually one wins, the other is driven to extinction (in Gause’s experiment with two species of Paramecium, competitive exclusion always led to survival of P. aurelia, elimination of P. caudatum (Figure 31.17); exclusion is less likely in nature, but does occur, as in takeover of large tracts of land in the American South by non-native kudzu vine, Figure 31.18).

14. Competition • 3. Competition may be avoided by coexisting species through resource partitioning (e.g., P. aurelia and P. bursaria manage to survive together in test tube by dividing up the habitat between them—P. aurelia is capable of colonizing lower, oxygen-depleted part of tube due to its symbiotic association with oxygen-producing algae).(Figure 31.19)

15. Warblers eating caterpillars on overlapping parts of a tree

16. Community relations • C. Predation and parasitism • 1.Predation refers to one freestanding organism feeding on parts or all of a second organism; predator-prey relationships are complex; their populations are linked, and may exhibit cyclical changes in abundance or decline (e.g., moose and gray wolves in Michigan’s Isle Royale National Park).

17. 2. Parasitism is a type of predation in which predator feeds on prey but does not immediately kill it; life cycles of parasite and host may be intertwined in complex ways (e.g., roundworm feeds on human host, moves from one organ system to another as it completes its life cycle; parasitic wasp lays eggs in caterpillar host, and for good measure injects virus, derived from its own DNA, to cripple host’s immune system).

18. Examples of co-evolving predator-prey relationships—camouflage in flatfish, worm-baiting spine in dorsal fin of frogfish (Figure 31.22). Examples of co-evolving predator-prey relationships—camouflage in flatfish, worm-baiting spine in dorsal fin of frogfish (Figure 31.22).

19. Community relations • D. Mutualism and commensalism are interactions that do not harm any of the partners, and may be beneficial to one (commensalism) or both (mutualism). Examples—mycorrhizal associations between fungi and plant roots, oxpeckers riding on rhinos and ridding them of ticks and flies (mutualism), birds nesting in trees, clownfish finding safe haven in poisonous tentacles of sea anemones (commensalism).

21. Chapter 32.3

22. Flow of energy Through Ecosystems

23. Energy flows through Ecosystems • Recall the laws of Thermodynamics. #1 Energy is never gained or lost, only transformed. #2 Energy flows spontaneously in one directions, from ordered to less ordered. • Heat is the ultimate destination of all energy. • Energy in an ecosystem starts with the sun and flows through a given ecosystem.

24. Model of an ecosystem showing the one-way flow of energy and the cycling of nutrients between autotrophic and heterotrophic organisms. Most of the energy originally fixed by the autotrophs is lost to the environment as metabolic heat.

25. Flow of Energy • Producers, consumers, trophic levels—production and consumption of energy in living world can be described in these terms: • 1. Photosynthetic organisms are producers. • 2. Organisms that eat photosynthetic organisms such as plants are consumers. • 3. Various feeding levels make up the trophic levels in a food chain, or in food webs, which are the more complex feeding patterns actually found in nature. Figure 32.11

27. Trophic Levels a.First trophic level—producers (photosynthesizers) b.Second trophic level—primary consumers (plant predators: herbivores and omnivores) c.Third trophic level—secondary consumers (herbivore predators: carnivores and omnivores) d. Fourth trophic level—tertiary consumers (organisms that feed on secondary consumers such as other carnivores and omnivores

28. Detrivores • Detrivores are a special class of consumers. • a.Feed on detritus (remains of dead organisms or cast-off material from living organisms). • b.Break down organic material, ultimately into inorganic components that can then be recycled through the ecosystem. • c.Example—decomposers, mostly fungi and bacteria. Figure 32.13

30. Food web

31. Energy Flow Energy flow through trophic levels—two questions are of interest to ecologists: How much of the Sun’s energy is harvested by the living world, and how much of this collected energy makes it through each successive trophic level? Available energy is lost at each step in the trophic chain, reaching very low levels at the top, so that a given ecosystem can sustain only a small number of large secondary or tertiary consumers (such as polar bears and lions).

33. Pyramids of biomass and energy flow