1 Interactions: Environments and Organisms Chapter 5

2 Ecological Concepts __________ - Study of ways organisms interact with each other and with their non- living surroundings. __________ - Study of ways organisms interact with each other and with their non- living surroundings. __________ - Everything that affects an organism during its lifetime. __________ - 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. ____________ - 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. _______ - Space an organism inhabits; defined by biological requirements of each particular organism. – Usually highlighted by prominent physical or biological features. Niche - __________________________________ Niche - __________________________________ – Includes all ways an organism affects organisms with which it interacts as well as how it modifies its physical surroundings. Fig. 5.3 Fig. 5.3

6 Ecological Niche

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

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

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

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

12 Evolutionary Patterns Extinction - Loss of entire species. 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. __________ - Two or more species can reciprocally influence the evolutionary direction of the other. – Grazing animals and grass species.

13 Kinds of Organism Interactions Predation - _____________________________________ _____________________________________ 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. 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. The more similar the competing species, the more intense the competition. Fig. 5.8 Fig. 5.8

16 Competition ______________________ - No two species can occupy the same ecological niche in the same place at the same time. ______________________ - 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. ___________ - 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. 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. ___________ - 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. 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. __________ - 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. 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. __________ - 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 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 ___________. 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 (2 nd 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. _________ - 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. _________ - 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. 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. 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 CO 2 and water back into the atmosphere.

29 Carbon Cycle

30 Nitrogen Cycle Cycling of nitrogen atoms between abiotic and biotic ecosystem components. Cycling of nitrogen atoms between abiotic and biotic ecosystem components. – Producers unable to use atmospheric N.  Must get nitrate NO 3 or ammonia NH 3. – ___________________ converts nitrogen gas N 2 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. 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 (N 2 ) which is ultimately released into the atmosphere. Denitrifying bacteria are able to (under anaerobic conditions) covert nitrite to nitrogen gas (N 2 ) which is ultimately released into the atmosphere.

32 Nitrogen Cycle

33 Phosphorus Cycle Phosphorus is not present in the atmosphere as a gas. 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: 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. Fossil fuel burning also increased amount of nitrogen available to plants. Fertilizer carried into aquatic ecosystems. Fertilizer carried into aquatic ecosystems.  Increase aquatic plant growth rate.  Lowered oxygen concentrations.

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

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