Chapter 15 & 16 notes
- 1. CHAPTER 15 & 16 NOTES “ POPULATIONS & ECOSYSTEMS”
- 2. I. HOW POPULATIONS GROW
- 3. A. Population – consists of all the individuals of a species that live together in one place at one time.
- 4. B. Survival of a population determined by 3 features: 1. population size - # of individuals in a population. Very small populations most likely to become extinct. 2. population density - # of individuals that live in a given area. 3. dispersion – way the individuals of a population are arranged in space.
- 5. Population growth – limited by predators , disease , and the availability of resources. 1. carrying capacity – population size that an environment can support. 2. density dependent factors – limited resources such as food, water 3. density independent factors – environmental conditions; weather, climate
- 6. II. HOW POPULATIONS EVOLVE
- 7. A. Hardy-Weinberg Principle – the frequencies of alleles in a population do not change unless evolutionary forces act on the population. 1. mutation 2. gene flow 3. nonrandom mating 4. genetic drift 5. natural selection – such as the mice populations – run-speed
- 8. III. CHARACTERISTICS OF ECOSYSTEMS
- 9. Ecology – the study of the interactions between organisms and their environment. Habitat – the place where a particular population of a species lives. Abiotic – physical factors of a habitat. Ex: soil, water, weather Biotic – living factors in a habitat. Ex: plants, animals, bacteria, fungi Community – many different species that live together in a habitat. Ecosystem – consists of a community and all of the physical factors of its habitat.
- 11. IV. CHANGES OF ECOSYSTEMS OVER TIME
- 12. Examples of new habitats and ecosystem development include: volcano forming a new island , glacier recedes and exposes bare rock , a fire burning all of the vegetation in an area. B. Pioneer specie s – first organisms to live in a new habitat. C. Succession – a somewhat regular progression of species replacement Primary succession – occurs where plants have not grown before. Ex: Glacier Bay, Alaska 2. Secondary succession – occurs in areas where there has been previous growth.
- 14. V. ENERGY FLOW IN AN ECOSYSTEM
- 15. Trophic level – the different energy levels in a food chain or pyramid. Food chain – the path of energy through the trophic levels of an ecosystem.
- 16. 1. First level – producers – green plants and algae 2. Second level– primary consumers (herbivores) 3. Third level – secondary consumers eat the herbivores (carnivores,omnivores) 4. Fourth level – tertiary consumers – (carnivores that consume carnivores) 5. At every level decomposers are found that break down the dead remains of all organisms. Ex: bacteria, fungi
- 17. C. Food web – a complicated, interconnected group of food chains.
- 18. D. The amount of energy available decreases as it passes from 1 trophic level to the next. Only about 10% of the energy from one level is passed on to the next level.
- 19. VI. BIOGEOCHEMICAL CYCLES
- 20. Cycles which pass nutrients from the nonliving environment to the living environment and back. 1. Water cycle – includes precipitation, evaporation, transpiration 2. Carbon cycle- includes respiration, combustion, and erosion . 3. Nitrogen cycle- 79 % of the atmosphere is nitrogen. Bacteria fix atmospheric nitrogen to make ammonia.