14.2 Community Interactions Definitions Competition: ecological relationship in which two organisms attempt to obtain the same resource. Predation: process

14.2 Community Interactions

Definitions• Competition: ecological relationship in which two organisms attempt

to obtain the same resource.

• Predation: process by which one organism hunts and kills another organism for food.

• Symbiosis: ecological relationship between members of at least two different species that live in direct contact with one another.

• Mutualism: ecological relationship between two species in which each species gets a benefit from the interaction.

• Commensalism: ecological relationship in which one species receives a benefit but the other species is not affected one way or another.

• Parasitism: ecological relationship in which one organism benefits by

harming another organism.


KEY CONCEPT Organisms interact as individuals and as populations.


Opener: Habitat or Niche

• Sister• House• Tree• Teacher• Bully• Mommy• Grandma• Cave


Competition and predation are two important ways inwhich organisms interact.

• Competition occurs when two organisms fight for thesame limited resource.

1. Intraspecificcompetition

2. Interspecificcompetition:


• Intraspecific competition: occurs when individuals of a particular species struggle against one another for limited resources. (ex. Bird species breeding: a typical male will share a particular territory with males of different bird species,but will not tolerate another male of its own species in the same area)

• Interspecific competition: occurs when two different species compete for a limited resource, such as space. (ex. In your lawn: grass, dandelions, and other plants compete for nutrients and water)


• Predation occurs when one organism captures and eats another.


• There are three major types of symbiotic relationships.

1. Mutualism: both organisms benefit


2. Commensalism: one organism benefits, the other is unharmed

Human Our eyelashes are home to tiny mitesthat feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle.

Demodicids Eyelash mites find all they need to survive in the tiny folliclesof eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope.

+

Organism benefits+

Ø

Ø Organism is not affected

Commensalism



3. Parasitism: one organism benefits, the other is harmed


Organism benefits0

_

Organism is not affected

Hornworm caterpillarThe host hornworm will eventually die as its organs are consumedby wasp larvae.

Braconid waspBraconid larvae feed on their host and release themselves shortly before reachingthe pupae stage of development.

_

Parasitism

+

0


• There are three major types of symbiotic relationships.– Parasitism meet their needs as ectoparasites (such

as leeches) and endopaasites (such as hookworms)


Mutualism

• The termite and its intestinal flagellate symbionts exemplify Obligate Mutualism: Neither organism can survive without the other.


Mutualism

• The Clown Fish and its Sea Anemone partner both benefit from the relationship: Nemo gets a safe home that protects him from predators, and he fiercely protects his sea anemone from predators. He also feeds the anemone. How cute is that?


Competition

• The Green Anole (Anolis carolinensis) is native to the southern United States. In the 1960's, The Brown Anole (Anolis sagrei) was introduced from Cuba. The two species vie for habitat and food resources, and it appears that the exotic Brown Anole has displaced the native Green Anole in some physical spaces, such as lower shrubbery and grass. The Green Anole generally lives higher up in the trees and foliage than the Brown Anole does. This result of competition is known as resource partitioning.


predation• This is possibly the most familiar type of symbiosis. The predator species (in

the illustration below, the Lion (Panthera leo)) kills and consumes the prey species (in this case, a Cape Buffalo (Syncerus caffer). You can no doubt think of dozens of other examples of predation. Predation has driven the evolution of some truly amazing phenomena, such as crypsis (camouflaging coloration), aposematism (warning coloration), mimicry, and other ways animals avoid being eaten.


Parasitism

• A parasite is an organism that takes up residence in or on a host organism and feeds on the host's body without killing it outright.Tape Worm.


Commensalism

• In this case, one species benefits from the presence of another, which is not affected by the presence of the first species. An example is the Cattle Egret. As large grazers move through the grass, they stir up insects. Cattle Egrets follow them and get a banquet. The large grazers are neither helped nor

harmed by the presence of the birds.


Homework

• Book: Read Section 14.3• Study Guide: 149-150


14.3 Definitions

• Population density: measure of individuals living in a defined area.

• Population dispersion: way in which individuals of a population are spread out over an area or volume.

• Survivorship curve: graph showing the surviving members of each age group of a population over time.


KEY CONCEPT Each population has a density, a dispersion, and a reproductive strategy.


Population density is the number of individuals that live in a defined area.

• Population density is a measurement of the number of individuals living in a defined space.

• Scientists can calculate population density.


• Population dispersion refers to how a population is spread in an area.

Geographic dispersion of a population shows how individuals in a population are spaced.

Clumpeddispersion

Uniformdispersion

Randomdispersion


• There are three types of dispersion.

1. clumped



2. uniform



3. random


Survivorship curves help to describe the reproductive strategy of a species.

• A survivorship curve is a diagram showing the number of surviving members over time from a measured set of births.


• Survivorship curves can be type I, II or III.– Type I—low level of infant mortality and an older

population– common to large mammals and humans– Type II—survivorship rate is equal at all stages of life– common to birds

and reptiles– Type III—very

high birth rate, very high infant mortality

– common to invertebrates and plants


Homework

• Book: Read 14.4• Study Guide: pg 151-152

Documents

14.2 Community Interactions Definitions Competition: ecological relationship in which two organisms attempt to obtain the same resource. Predation: process