1 Community Ecology Chapter 56

2 Biological Communities Community: all the organisms that live together in a specific place –Evolve together –Forage together –Compete –Cooperate

3 Individualistic concept: a community is a group of species that happen to occur together at one place –species respond independently to changing environmental conditions –The composition of a Community can change Biological Communities

4 Ecological Niche Niche: An Organism’s way of life –Habitat –Food –Temp. range –Reproduction

5 Ecological Niche Fundamental niche: the entire niche that a species is capable of using. Realized niche: actual niche in which the species can establish a stable population

6 Ecological Niche study of barnacles

7 Ecological Niche causes of niche restriction –Competition –Predators –Absence of pollinators –Presence of herbivores Billock

8 Ecological Niche Principle of competitive exclusion: no two species can occupy the same niche when resources are limited Species may divide up the resources, (resource partitioning) natural selection can then lead to adaptive radiation

9 Resource partitioning among sympatric lizard species

10 Ecological Niche Character displacement in Darwin’s finches

11 Predator-Prey Predation and coevolution 1.Predation provides strong selective pressure on the prey population 2.Features that decrease the probability of capture are strongly favored 3.Predator populations counteradapt to continue eating the prey  Coevolution race

12 Examples of prey adaptations: Chemical defenses Camouflage Warning coloration mimicry

13 Species Interactions Symbiosis: two or more kinds of organisms interact in more-or-less permanent relationships All symbiotic relationships carry the potential for coevolution Three major types of symbiosis –Commensalism –Mutualism –Parasitism

14 Species Interactions Commensalism benefits one species and is neutral to the other –Spanish moss: an epiphyte hangs from trees

Shark and Pilot Fish

Barnacles and Whales

17 Species Interactions Mutualism benefits both species Coevolution: flowering plants and insects Ants and acacias –Acacias provide hollow thorns and food –Ants provide protection from herbivores

Human Intestine and E.Coli

Zebra and Oxpecker Bird

20 Species Interactions Parasitism benefits one species at the expense of another Can be external or internal parasites

21 Species Interactions External parasite: the yellow vines are the flowering plant dodder, it is a parasite that obtains its food from the host plant it grows on

Heartworm and Dogs

Mistletoe and Mesquite Tree

24 Species Interactions Ecological processes can interact –Predation reduces competition Superior competitors become more numerous and attract predators This allows other species to survive when they could have been out competed

25 Species Interactions Starfish eat barnacles, allowing other species to thrive instead of being crowded out by the explosive population of barnacles

26 Keystone species: species whose effects are greater than expected Examples: –Sea star predation on barnacles –Beaver ponds –Top predators Species Interactions

27 Species Interactions Beavers construct dams and transform flowing streams into ponds, creating new habitats for many plants and animals