CHAPTER 15 & 16 CHAPTER 15 & 16 NOTESNOTES

““POPULATIONS & POPULATIONS & ECOSYSTEMS”ECOSYSTEMS”

I. HOW POPULATIONS GROWI. HOW POPULATIONS GROW

A. A. PopulationPopulation – consists of all the individuals – consists of all the individuals of a of a speciesspecies that live together in one place at that live together in one place at one time.one time.

B. Survival of a B. Survival of a populationpopulation determined by 3 determined by 3 features: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.

C. 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

II. HOW POPULATIONS II. HOW POPULATIONS EVOLVEEVOLVE

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

III. CHARACTERISTICS OF III. CHARACTERISTICS OF ECOSYSTEMSECOSYSTEMS

A. Ecology – the study of the interactions between organisms and their environment.

B. Habitat – the place where a particular population of a species lives.

1. Abiotic – physical factors of a habitat.Ex: soil, water, weather

2. Biotic – living factors in a habitat.

Ex: plants, animals, bacteria, fungi

C. Community – many different species that live together in a habitat.

D. Ecosystem – consists of a community and all of the physical factors of its habitat.

Community/EcosystemCommunity/Ecosystem

IV. CHANGES OF ECOSYSTEMS IV. CHANGES OF ECOSYSTEMS OVER TIMEOVER TIME

A. 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 species – first organisms to live in a new habitat.

C. Succession – a somewhat regular progression of species replacement

1. 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.

Examples of SuccessionExamples of Succession

V. ENERGY FLOW IN AN V. ENERGY FLOW IN AN ECOSYSTEMECOSYSTEM

A. Trophic level – the different energy levels in a food chain or pyramid.

B. Food chain – the path of energy through the trophic levels of an ecosystem.

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

C. Food web – a complicated, interconnected group of food chains.

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.

VI. BIOGEOCHEMICAL VI. BIOGEOCHEMICAL CYCLESCYCLES

A. 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.