1. Intro to Ecology TURK CHAPTERS 18-20

2. Levels of organization  biosphere  ecosystem  community  population  organism

3. Ecosystem components  Biotic and Abiotic Factors  Both biotic, or living, factors and abiotic, or nonliving, factors influence organisms. Examples of abiotic factors are climate, sunlight, and pH.  A niche is a way of life, or a role in an ecosystem.

4. Producers and consumers  Most producers are photosynthetic and make carbohydrates by using energy from the sun.  Consumers obtain energy by eating other organisms and include herbivores, omnivores, carnivores, detritivores, and decomposers.

5. Energy Flow  Food Chains and Food Webs  A single pathway of energy transfer is a food chain.  A network showing all paths of energy transfer is a food web.

6. Energy flow cont…  Energy Transfer  Ecosystems contain only a few trophic levels because there is a low rate of energy transfer between each level.

7. Water cycle  Key processes in the water cycle are evaporation, transpiration, and precipitation.

8. Carbon cycle  Photosynthesis and cellular respiration are the two main steps in the carbon cycle.

9. Nitrogen Cycle  Nitrogen-fixing bacteria are important in the nitrogen cycle because they change nitrogen gas into a usable form of nitrogen for plants.

10. Phosphorus cycle  In the phosphorus cycle, phosphorus moves from phosphate deposited in rock, to the soil, to living organisms, and finally to the ocean.  Phosphorus is needed to make DNA, RNA, and proteins.

11. Populations  A population is a group of organisms that belong to the same species and live in a particular place at the same time.  Populations can be measured in terms of size, density, dispersion, growth rate, age structure, and survivorship.

12. Populations cont…  Population Size  A population’s size is the number of individuals that the population contains.  Population Density  Density is a measure of how crowded the population is.  Dispersion  Dispersion describes the distribution of individuals within the population and may be random, uniform, or clumped.

13. Three Population Dispersion Patterns

14. Population Dynamics  Age Structure  A population’s age structure indicates the percentage of individuals at each age.  Patterns of Mortality  Populations show three patterns of mortality or survivorship curves :  Type I (low mortality until late in life)  Type II (constant mortality throughout life)  Type III (high mortality early in life followed by low mortality for the remaining life span).

15. Population Growth Rate  the growth rate of a population is the amount by which a population’s size changes in a given time.  Population Size  Birth rate - death rate = growth rate  The exponential model describes perpetual growth at a steady rate in a population.  The model assumes constant birth and death rates and no immigration or emigration.

16. Population Growth Rate cont…  In the logistic model, birth rates fall and death rates climb as the population grows.  When the carrying capacity is reached, the number of individuals the environment can support is reached and population growth becomes stable.

17. Population limiting factors  Population-limiting factors, such as competition, are density-dependent because the effect on each individual depends on the number of other individuals present in the same area.  Population-limiting factors, such as bad weather and fires, are density-independent because the effect on each individual does not depend on the number of other individuals present in the same area.

18. Small populations  Small populations have low genetic diversity and are subject to inbreeding, so they are less likely to adapt to environmental changes.

19. Human Population Growth  Around 1650, improvements in hygiene, diet, and economic conditions further accelerated population growth.  After World War II, the human population grew at the fastest rate in history, largely because of better sanitation and medical care in poorer countries.

20. Human Population Growth

21. Demographic Transition  Today, developing countries have faster human population growth and lower standards of living than developed countries do.  Human populations have undergone rapid growth, yet in some developed countries, populations have stopped growing.  The demographic transition model shows how these population changes happen.

22. Demographic Transition

23. Predation  Predation is an interaction in which one organism (the predator) captures and eats all or part of another individual organism (the prey).  Predator Adaptations  Predators have adaptations to efficiently capture prey, whereas prey species have adaptations to avoid capture.  Adaptations in Animal Prey  Mimicry is an adaptation in which a species gains an advantage by resembling another species or object.  Adaptations in Plant Prey  Many plants produce secondary compounds as a chemical defense.

24. Competition  Competitive Exclusion  Competition may cause competitive exclusion, the elimination of one species in a community.

25. Competition  Character Displacement  Competition may drive the evolution of niche differences among competitors. This evolution of differences in a characteristic due to competition is called character displacement.  Resource Partitioning  Differential resource use to avoid competition is called resource partitioning.

26. Symbiosis  Parasitism  In parasitism, one species (the parasite) feeds on, but does not always kill, another species (the host).  Mutualism  In mutualism, both interacting species benefit.  Commensalism  In commensalism, one species benefits, and the other is not affected.

27. Species richness  Species richness is the number of species in a community.  Species evenness is the relative abundance of each species.  Latitude and Species Richness  In general, species richness is greatest near the equator, and larger areas support more species.

28. Species richness  Species Interactions and Species Richness  Species interactions such as predation can promote species richness.  Community Stability and Species Richness  Disturbances can alter a community by eliminating or removing organisms or altering resource availability.  Species richness may improve a community’s stability.  Areas of low species richness may be less stable in the event of an ecological disturbance.

29. Succession  Ecological succession is a change in the species composition of a community over time.  Primary Succession  Primary succession is the assembly of a community on newly created habitat.  Primary succession occurs in areas that have been recently exposed to the elements and lack soil.  Primary succession typically proceeds from lichens and mosses to a climax community.

30. Succession  Secondary Succession  Secondary succession is the change in an existing community following a disturbance.  Secondary succession occurs in areas where the original ecosystem has been cleared by a disturbance.  The community proceeds through a predictable series of stages until it reaches a stable end point, called the climax community.  Secondary succession typically proceeds from weeds to a climax community.

31. Succession