Interactions: Environments and Organisms

1. Interactions: Environments and Organisms Chapter 5

2. Ecological Concepts • __________ - Study of ways organisms interact with each other and with their non-living surroundings. • __________ - Everything that affects an organism during its lifetime. • Biotic - ___________________ • Abiotic - ______________________

3. Levels of Organization in Ecology

4. Ecological Concepts • ____________ - Any factor whose shortage or absence restricts species success. • Range of Tolerance - Range of conditions an organism can survive in. • Temperature • pH • DO

5. Habitat and Niche • _______ - Space an organism inhabits; defined by biological requirements of each particular organism. • Usually highlighted by prominent physical or biological features. • Niche - __________________________________ • Includes all ways an organism affects organisms with which it interacts as well as how it modifies its physical surroundings. • Fig. 5.3

6. Ecological Niche

7. Genes Population and Species • ________ - Distinct pieces of DNA that determine the characteristics an organism displays. • Population - ________________________________________________________________________ • Contains more kinds of genes than any single individual within the population.

8. Genes Population and Species • Species - ________________________________________________________________________________________________________________________________________________ • Working definition that only applies to organisms that sexually reproduce. • Some species are easy to recognize, while others are more difficult.

9. Natural Selection • ______________ - Process that determines which individuals within a species will reproduce and pass their genes to the next generation. • Conditions: • Individuals within a species show genetically determined variation. • Organisms within a species typically produce huge numbers of offspring, most of which die.

10. Natural Selection Conditions • Excess number of individuals results in a shortage of specific resources. • Due to individual variation, some individuals have a greater chance of obtaining needed resources and thus have a greater likelihood of survival and reproduction. • As time passes, percentage of individuals showing favorable variations will increase while percentage showing unfavorable variations will decrease.

11. Evolutionary Patterns • __________ - A change in the kinds of organisms that exist and in their characteristics. • Ex. Building tolerance to pesticides. • Speciation - ________________________________________________________________________ • Thought to occur as a result of a species dividing into two reproductively isolated subpopulations.

12. Evolutionary Patterns • Extinction - Loss of entire species. • Of estimated 500 million species believed to have ever existed on earth, 98-99% have gone extinct. • __________ - Two or more species can reciprocally influence the evolutionary direction of the other. • Grazing animals and grass species.

13. Kinds of Organism Interactions • Predation - __________________________________________________________________________ • Prey adaptation is manifested in a higher reproduction rate. • Fig. 5.7

14. Kinds of Organism Interactions • Prey species benefits by eliminating non-adaptive genes from the gene pool. • Poorly adapted predators are less likely to obtain food and thus pass on non-adaptive genes.

15. Competition • Competition - Two organisms strive to obtain the same limited resource, and both are harmed to some extinct. • ___________ - Members of same species competing for resources. (Mice for Cheese) • ___________- Members of different species competing for resources. (Fox & Hawk for Mice) • The more similar the competing species, the more intense the competition. • Fig. 5.8

16. Competition • ______________________ - No two species can occupy the same ecological niche in the same place at the same time. • Less fit species must evolve into a slightly different niche.

17. Symbiotic Relationships • ___________ - Close, physical relationship between two different species. At least one species derives benefit from the interaction. • Parasitism - __________________________________________________________________________________________________________________ • Ectoparasites - Live on host’s surface. • Fleas • Endoparasites - Live inside host. • Tapeworms

18. Symbiotic Relationships • Commensalism - One organism benefits while the other is not affected. • Remoras and Sharks • ___________ - Both species benefit. Obligatory in many cases as neither can exist without the other. • Mycorrhizae

19. Community and Ecosystem Interactions • Community - Assemblage of all interacting species of organisms in an area. • __________ - Defined space in which interactions take place between a community, with all its complex interrelationships, and the physical environment.

20. Major Roles of Organisms in Ecosystems • Producers - Organisms able to use sources of energy to make complex organic molecules from simple inorganic molecules in the environment. • Ex. Grasses, Trees, Moss, Ferns

21. Roles of Organisms • __________ - Consume organic matter to provide themselves with energy and organic matter necessary for growth and survival. • Primary Consumers • Herbivores (plants) • Secondary Consumers • Carnivores (animals) • Omnivores (plants and animals) • Scavengers (dead animals)

22. Roles of Organisms • _______________ • Digest organic molecules in detritus into simpler organic compounds, and absorb soluble nutrients. (Bacteria and Fungi) • Use non-living organic matter as source of energy. • Keystone Species • Play critical role in maintenance of specific ecosystems. • Bison in American Tall Grass Prairie

23. Energy Flow Through Ecosystems • Each step in the flow of energy through an ecosystem is known as a ___________. • As energy moves from one trophic level to the next, most of the useful energy (90%) is lost as heat (2nd Law of Thermodynamics). • Because energy is difficult to track, biomass (weight of living material) is often used as a proxy.

24. Energy Flow Through an Ecosystem

25. Food Chains and Food Webs • _________ - Passage of energy from one trophic level to the next due to one organism consuming another. • Some chains rely on detritus. • _________ - Series of multiple, overlapping food chains. • A single predator can have multiple prey species at the same time. • Fig. 5.15

26. Food Chain

27. Nutrient Cycles in Ecosystems • Organisms are composed of molecules and atoms that are cycled between living and non-living portions of an ecosystem. • Biogeochemical Cycles - another name for nutrient cycles.

28. Carbon Cycle • Carbon and oxygen combine to form carbon dioxide. • Plants use carbon dioxide during photosynthesis to produce sugars. • Plants use sugars for plant growth. • Herbivores eat plants, and incorporate molecules into their structure. • Respiration breaks down sugars releasing CO2 and water back into the atmosphere.

29. Carbon Cycle

30. Nitrogen Cycle • Cycling of nitrogen atoms between abiotic and biotic ecosystem components. • Producers unable to use atmospheric N. • Must get nitrate NO3 or ammonia NH3. • ___________________ converts nitrogen gas N2 into ammonia. Legumes (Roots) • Plants construct organic molecules. • Eaten by animals. • Drains soil of Nitrogen. • Decomposers also break down nitrogen-containing molecules releasing ammonia.

31. Nitrogen Cycle • Nitrifying bacteria are able to convert ammonia to nitrite, which can be converted to nitrate. • Denitrifying bacteria are able to (under anaerobic conditions) covert nitrite to nitrogen gas (N2) which is ultimately released into the atmosphere.

32. Nitrogen Cycle

33. Phosphorus Cycle • Phosphorus is not present in the atmosphere as a gas. • Phosphorus compounds released by erosion and become dissolved in water. • Plants use phosphorus to construct necessary molecules. • Animals gain necessary P via herbivory. • Decomposers recycle into soil.

34. Phosphorus Cycle

35. Human Impact on Nutrient Cycles • Two activities caused significant changes in carbon cycle: • Burning of fossil fuels. (2001 – IPCC Report) • Converting forests to agricultural land. • Fossil fuel burning also increased amount of nitrogen available to plants. • Fertilizer carried into aquatic ecosystems. • Increase aquatic plant growth rate. • Lowered oxygen concentrations.

36. Review • Ecological Concepts • Habitat and Niche • Natural Selection and Evolution • Organism Interactions • Predation • Competition • Community and Ecosystem Interactions • Roles of Organisms • Energy Flow Through Ecosystems • Nutrient Cycles in Ecosystems