Ecology

Ecology  The study of the interactions of organisms with their physical environment.

Population  A group of individuals on one species living in one area who have the ability of interbreeding and interacting with each other.

Community  Consists of all the organisms living in one area.

Ecosystem  All organisms in a given area as well as the abiotic (nonliving) factors with which they interact.

Abiotic Factors  Nonliving  Temperature, water, sunlight, wind, rocks, soil

Biosphere  Global Ecosystem

Five Properties of a Population  Size  Density  Dispersion  Survivorship Curves  Age Structure Diagrams

1. Size  The total number of individuals in a population.

2. Density  Number of individuals per unit area or volume.  Scientists use sampling techniques to estimate the number of organisms living in one area.  Mark and recapture.

3. Dispersion  Pattern of spacing of individuals within the area the population inhabits.  Clumped  Uniform  Random

Dispersion: Clumped  The most common pattern.  i.e. Fish traveling in schools.

Dispersion: Uniform  Even distribution of population in environment.  i.e. some plants may secrete toxins that keep away other plants that would compete for limited resources.

Dispersion: Random  Absence of any special attractions or repulsions.  i.e. trees can be spaced randomly in a forest.

4. Survivorship Curves  Survivorship or mortality curves show the size and composition of a population.  Type 1  Type 2  Type 3

Type 1  Show organisms with low death rates in young and middle age.  High death rates in old age.  Parenting accounts for the high survival rates of the young.  i.e. Humans

Type 2  Describe a species with a death rate that is constant over the life span.  i.e. Hydra, Reptiles, Rodents

Type 3  Very high death rate among the young, but then shows that death rates decline for those few individuals that have survived to a certain age.  Fish and vertebrates that release thousands of eggs.

Age Structure Diagrams  Diagrams that show the relative number of individuals at each age.

Undeveloped Population  “Pyramid Shape”  Normally half the population is under 20 years of age  The population in 20 years will be enormous.

Developed Population  Stable Population  Zero Population Growth  Number of people at each age group is the same, and the birth and death rates are equal.

Carrying Capacity  The limit of the number of individuals that can occupy one area at a particular time.  Limiting factors that limit population growth  Density-Dependent  Density-Independent

Density-Dependent  Factors that increase directly as the population density increases  Competition for food, buildup of wastes, predation, and disease.

Density-Independent  Factors whose occurrence is unrelated to the population density.  Earthquakes, storms, and naturally occurring fires and floods.

Competition  Competitive exclusion principle  Two species cannot coexist in a community if they share a niche (they use the same resources)  One species will drive the other to extinction.

Predation  Refers to one animal eating another, or an animal eating plants.  Plants have evolved spines, thorns, and chemical poisons.  Animals have developed active defenses: Hiding, fleeing, or defending themselves

Aposematic Coloration  “Warning Coloration”  Very bright, often red or orange, coloration of poisonous animals as a warning that possible predators should avoid them.

Batesian Mimicry  “copycat” coloration where one harmless animal mimics the coloration of one that is poisonous.  Monarch and Viceroy Butterfly

Mullerian Mimicry  Two or more poisonous species resemble each other and gain an advantage from their combined numbers.  Predators learn more quickly to avoid prey with that appearance.

Mutualism  A symbiotic relationship where both organisms benefit (+/+)  i.e. bacteria that live in the human intestine and produce vitamins.

Commensalism  Symbiotic relationship where one organism benefits and one is unaware of the other organism (+/0).  i.e. barnacles that attach to the underbelly of whales gain access to a variety of food sources as the whale swims.

Parasitism  One organism, the parasite, benefits while the host is harmed.  i.e. Tapeworm in the intestine.

Food Chain  Pathway along which food is transferred from one trophic or feeding level to another.  Energy moves from producers to herbivores to the carnivores.

Food Web

Producer  Convert light energy to chemical bond energy  Have the greatest biomass of any trophic level  Green Plants

Primary Consumers  Herbivores  Eat the producers  i.e. grasshoppers, zooplankton

Secondary Consumers  Carnivores  Eat the primary consumers  Examples: Frogs, small fish

Tertiary Consumers  Carnivores  Eat Secondary Consumers  Top of Food Chain  Have the smallest biomass of any other trophic level  Least stable  i.e. Hawk

Decomposers  Bacteria and Fungi  Recycle nutrients back into the soil to nourish plants.  Without decomposers there would be no life.