Populations and Communities

Activity 37 pg. 292-296

Studying Populations Population= all living things e.g. Frogs in local pond, balsam firs in local forest. Must all be same species, in shared space. Shows how species evolve.

Population Size Number individuals it contains Varies with time due to births, deaths, immigration, emigration

Births + immigration vs. Deaths + emigration  = population incr.  = population decr. = = stable

PG. 310 Q 1-4

Measuring a Population 1) Counting Individuals- count ALL individuals in certain area 2) Count by sample Area- counting individuals in randomly selected areas called quadrants Pop. Size = Avg. # per section x total study area Area of selection

3) Mark and Recapture- to estimate size of mobile animals e.g. Birds Pop. size = # marked x total # captured 2nd time # marked animals recaptured

Activity 38 pg. 297-302

Population Density The average # within given area Density will vary with habitat (food, water, climate, predators, disease etc.) Population density = # individuals area or volume occupied

Pg 310-11 Q5-9

Population Distribution 1) clumped = groups- when certain areas of habitat = better living conditions e.g. Herds

Population Distribution 2) uniform = distributed evenly- when fighting for resources e.g. Territory

Population Distribution 3) random = no pattern- because cannot clump or spread out e.g. plants

McDonald’s Restaurants Random Clumped

Ecological Factors Abiotic- non living factors- physical or chemical aspects e.g. pH of water Biotic- living factors- food source, predators Intensity of factor determines effect on population

Limiting Factors If it reduces or prevents growth 1) if absent from habitat e.g. Sunlight cut off to plant = no photosynthesis 2) in excess e.g. Too much rain = roots of plant rots 3) if insufficient quantities e.g. Frogs get disease so less, snake population will be affected

Biological Cycles Populations have periods of growth and decline Populations of food source and predators are very closely related

Pg 311-12 Q 10-15

Activity 39 pg 303-309

Studying Communities

Biodiversity Recording of all the types and numbers of species living in a community Species richness = # species in a community e.g. # blonde grade 10 girls at C.V.R. Relative abundance = # each species in relation to total # individuals in the community e.g. # blonde grade 10 girls compared to the total population of C.V.R.

Interaction Between Individuals in a Community Individuals do not live in isolation: 1) Competition: certain resources are limited E.g. Food source, water source Intraspecific- competition between same species Interspecific- competition between different species

2) Predation- one organism feeding off another Deer eating grass, lioness hunting a gazelle Predator feeds off another Prey is the food Parasites = takes food from host Host supplies the food

3) Mutualism- interaction benefits both species. - anemone and clown fish- fish acts as bait to anemone's food, anemone's sting protects clown fish

4) Commensalism- benefits one without affecting another Bird build s nest in a tree

Effect of interactions between populations and their densities Type of interaction Effect on population A Effect on population B Competition - Predation and Parasitism + Mutualism Commensalism

Pg 312-313 Q 16-19, A-C