CHAPTER. Evolution and Community Ecology

Transcription

1 CHAPTER 5 Evolution and Community Ecology

2 Lesson 5.1 Evolution Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered.

3 Lesson 5.1 Evolution Evolution (change over time) and Natural Selection QuickTime and a decompressor are needed to see this picture. A starting population of fish. Genes control the color and pattern of the fish s scales. Gene: Sequence of DNA that codes for a particular trait Gene pool: All the genes present in a pop Biological evolution: change in a pop s gene pool over time

4 Lesson 5.1 Evolution Mechanisms of Biological Evolution: Mutation and Migration QuickTime and a decompressor are needed to see this picture. Mutation Change in DNA that can give rise to variation among indivs Migration (gene flow) Movt of individuals into (immigration) or out of (emigration) a pop changes gene pool (gene flow)

5 Lesson 5.1 Evolution Mechanisms of Biological Evolution: Genetic Drift and Natural Selection QuickTime and a decompressor are needed to see this picture. Genetic Drift Evolution that occurs by chance Natural Selection Process by which traits useful for survival & reprod are passed on more frequently than those that are not

6 Lesson 5.1 Evolution Conditions of Natural Selection QuickTime and a decompressor are needed to see this picture. QuickTime and a decompressor are needed to see this picture. (1) Organisms produce more offspring than can survive struggle for existence (2) Indivs vary in characteristics, some of which are heritable. Did You Know? Darwin privately researched natural selection for two decades before publishing On the Origin of Species. (3) Indivs vary in fitness, or reproductive success. (adaptations increase org fitness level)

7 Lesson 5.1 Evolution Artificial Selection Selection under human direction Chosen & bred animals & plants with beneficial traits.

8 Lesson 5.1 Evolution Process by which new species are generated Speciation Can occur in a number of different ways; the most important way is called allopatric speciation (geographic sep of pops) QuickTime and a decompressor are needed to see this picture. Has resulted in every form of life on Earth today & in the past Allopatric Speciation

9 Lesson 5.1 Evolution Trilobites Marine arthropods that went extinct at the end of the Permian period. Did You Know? During the Permo-Triassic extinction 250 million years ago, 70% of all land species and 90% of all marine species went extinct. Extinction Disappearance of species from Earth Generally occurs gradually, 1 species at a time, when envtal conditions change more rapidly than species can adapt 5 known mass extinction events, each of which wiped out a large proportion of Earth s species.

10 Lesson 5.2 Species Interactions The zebra mussel has completely displaced 20 native mussel species in Lake St. Clair.

11 Lesson 5.2 Species Interactions The Niche Describes org s use of resources & functional role in a community Affected by an organism s tolerance its ability to survive & reproduce under changing environmental conditions Often restricted by competition

12 Lesson 5.2 Species Interactions Organisms compete when they seek the same limited resource. In rare cases, one species can entirely exclude another from using resources. Competition To reduce competition, species often partition resources, which can lead to character displacement.

13 Lesson 5.2 Species Interactions Predation (+/ ) Predator hunts, kills, & consumes prey Causes cycles in predatory & prey population sizes Defensive traits: camouflage, mimicry, & warning coloration have evolved in response to predator-prey interactions. Some predator-prey relationships are ex of coevolution, the process by which 2 species evolve in response to changes in each other. Rough-Skinned Newt Did You Know? A single roughskinned newt contains enough poison to kill 100 people. Unfortunately for the newt, its predator, the common garter snake, has coevolved resistance to the toxin.

14 Lesson 5.2 Species Interactions Parasitism and Herbivory (+/ ) Parasitism: 1 org (the parasite) relies on another (the host) for nourishment or for some other benefit Hookworm (a parasite) Herbivory: An animal feeding on a plant Did You Know? One study of Pacific estuaries suggests that parasites play an important role in keeping these ecosystems healthy by controlling host populations.

15 Lesson 5.2 Species Interactions Mutualism (+/+) and Commensalism (+/0) Mutualism: a relationship in which 2 or more species benefit Lichen: a symbiotic relationship between a fungus and a photosynthetic partner, such as an alga Commensalism: a relationship in which 1 species benefits while the other is unaffected Did You Know? Symbiosis describes a longlasting and physically close relationship between species in which at least one species benefits.

16 Lesson 5.3 Ecological Communities The sun provides the energy for almost all of the ecological communities and species interactions on Earth.

17 Lesson 5.3 Ecological Communities Primary Producers (Autotrophs) Capture NRG from sun/chemicals & store it in the bonds of sugars, making it available to rest of community NRG from the sun is captured by plants, algae, or bacteria thru photosynthesis. NRG from chemicals captured by some bacteria thru chemosynthesis. Did You Know? Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.

18 Lesson 5.3 Ecological Communities Consumers (Heterotrophs) Rely on other organisms for NRG & nutrients Herbivores: plant-eaters Carnivores: meat-eaters Omnivores: combo-eaters Detritivores and decomposers: recycle nutrients w/in the ecosystem by breaking down nonliving organic matter Use oxygen to break bonds in sugar & release its NRG thru cellular respiration (primary producers do this, too) California Condor Did You Know? Scavengers, such as vultures and condors, are just large detritivores.

19 Lesson 5.3 Ecological Communities Energy in Communities Organism s rank in a feeding hierarchy is its trophic level. Primary producers always occupy 1 st trophic level of any community. In general, only about 10% of the NRG avail at any trophic level is passed to the next; most of the rest is lost to the envt as heat. QuickTime and a decompressor are needed to see this picture. Pyramid of Energy

20 Lesson 5.3 Ecological Communities Numbers & Biomass in Communities A trophic level s biomass = mass of living tissue it contains. In general, there are more orgs & greater biomass at lower trophic levels than higher ones.

21 Lesson 5.3 Ecological Communities Food Chains and Webs Food chain: Linear series of feeding relationships Food web: Shows the overlapping and interconnected food chains present in a community QuickTime and a decompressor are needed to see this picture.

22 Lesson 5.3 Ecological Communities Keystone Species Species that have strong and/or wide-reaching effects on a community Removal of keystone species can significantly alter the structure of community.

23 Lesson 5.4 Community Stability A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages. Invasive kudzu

24 Lesson 5.4 Community Stability Ecological Disturbances Community in equilibrium is generally stable & balanced, w/ most populations at/or around carrying capacity. Disturbances/changes in envt can throw a community into disequilibrium. Severe disturbances cause permanent changes to a community & initiate a predictable series of changes = succession. Forest fire

25 Lesson 5.4 Community Stability Primary Succession No traces of the original community remaining, including vegetation and soil Pioneer species (lichens):1 st to colonize. Envt changes as new species move in, adding nutrients & generating habitat.

26 Lesson 5.4 Community Stability Secondary Succession Occurs when disturbance dramatically alters a community but does not completely destroy it Common after disturbances such as fire, logging, or farming Occurs significantly faster than primary succession

27 Lesson 5.4 Community Stability Succession in Water Primary aquatic succession occurs when an area fills w/ water for the 1 st time. Disturbances such as floods or excess nutrient runoff can lead to secondary aquatic succession.

28 Lesson 5.4 Community Stability Climax Communities Ecologists once thought succession leads to stable climax communities. Today, ecologists see communities as temporary, ever-changing associations of species. Communities influenced by many factors & constant disturbances. Beech-maple forest, a classic climax community

29 Lesson 5.4 Community Stability Invasive Species Nonnative organisms that spread widely in a community A lack of limiting factors such as predators, parasites, or competitors enables their population to grow unchecked. Not all invasive species are harmful. Did You Know? Although the European honeybee is invasive to North America, it is beneficial because it pollinates our agricultural crops.