Populations and Communities

Chapter 1 Sections 1-3

Ecology

• The scientific study of interactions among organisms and between organisms and their environment, or surroundings.

• Origin of the word:– Greek word – oikos (which means “house”)– Thus- ecology means the study of natures house

Levels of Organization

• Species: group of organisms so similar to one another that they can breed and produce fertile offspring

• Population: groups of individuals that belong to the same species that live in the same area

• Communities: assemblages of different populations hat live together in a defined area

• Ecosystem: the community of organisms that live in a particular area, along with their nonliving (abiotic) surroundings

Habitat and Biotic/Abiotic Factors

• Habitat: An environment that provides an organism with its needs to live, grow and reproduce.

• Biotic Factors: the living parts of a habitat– Ex: animals and plants

• Abiotic Factors: the nonliving part of a habitat– Ex: temperature, sunlight, water

Determining Populations - Methods

1. Direct observation: counting all the members in an area

2. Indirect observation: counting the “signs” of an organism and estimating the population (ex: nests of an animal)

3. Sampling: approximation of a population by counting a smaller area

4. Mark and Recapture: Catch a number of individuals, mark them. Return to the area at a later date and catch individuals again. Mathematically compare the number originally marked to the number recaptured.

Changes in Population Size• Birth rate/death rate: the number of individuals

that are born or die over a specific time Birth Rate > Death Rate = Pop. Increases Death Rate > Birth Rate = Pop Decreases

• Immigration: individuals moving INTO a population• Emigration: individuals leaving or EXITING a

population

Limiting Factors in Population Size

1. Food and water: Because organisms require food and water, the amount of resources will determine the populations carrying capacity

2. Space: organisms need a certain amount of space to thrive, if this space is not available the population will decrease

3. Weather: conditions, such as temperature or rainfall, can limit populations.

Carrying Capacity: the largest population that an area can support

What options an organism have if it’s needs are not met in it’s current

environment?

1. migrate to better place2. adapt to fit environment3. die

Interactions Among Living Things• Natural Selection: the process that occurs

over time where a characteristic that makes an individual better suited to their environment becomes common

• Adaptation: a behavior and/or physical characteristic that allows an organism to live successfully– Ex: finches (beaks), fish (gills)

Types of Animal Interactions:

•Competition•Predation•Symbiosis

Competition• Competition occurs when two or more

individuals seek to utilize the same resourceSiafu or Driver Ants (Hymenoptera) of Africa out

compete and consume everything that crosses its path, even cows!!!

Predation

• Predation describes an interaction where a predator species kills and eats other organisms, known as prey.

• Predation can greatly effect population size– Too many predators causes a decrease in prey

population which then causes a decrease in predators.

– Predators/prey populations rise and fall in cycles

Adaptations of Predators and PreyPredators have adapted to become better and more

efficient– Ex. Hunting at night, speed, eyes in the front of their

head

Prey have also adapted to avoid being eaten– Mimicry– False coloring– Warning colors– Camouflage

Symbiosis

• Symbiosis is a close ecological relationship between the individuals of two or more species that benefits at least one of the species

• Mutualism, commensalism, parasitism,

Mutualism

• Mutualism is an association between organisms of two different species in which each member benefits.

• Ants (Hymenoptera) protect the aphids (Aphididae) and the aphids provide honeydew for the ants

Commensalism

• Commensalism is a symbiotic relationship between two organisms of different species in which one derives some benefit while the other is unaffected.

• Pseudoscorpions hitching ride on a fly’s (Diptera) leg

Parasitism• Parasitism is a form of symbiosis in which one

species benefits at the expense of another species; similar to predation, but acts more slowly than predators and may not always kill the host.

• Parasitized caterpillar (Lepidoptera), covered with wasp (Hymenoptera) pupae which have consumed all internal tissue except vital organs