Chapter 54 Community Ecology Community Ecology The study

Chapter 54 Community Ecology

Community Ecology • The study of the interactions between the species in an area.

Interspecific Interactions • Interaction between species. • May be positive, negative, or neutral (in regards to fitness) • Ex: Predation Mimicry Competition Symbiosis

Predation (+/-) • Predator and prey relationships. • Ex – Lynx and Hares

Herbivory (+/-) • When an organism eats parts of a plant or algae. • Herbivore – may have special adaptations to find their prey. • Plants – may have adaptations to avoid being eaten.

Predation/Herbivory • Often results in interesting defenses or adaptations. • Ex: • Cryptic coloration • Aposematic coloration

Cryptic Coloration • A passive defense where the prey is camouflaged against its environment.

Aposematic Coloration • The use of poison arrow frogs conspicuous colors in toxic or unpalatable organisms to warn off predators.

Mimicry • Defense mechanism where the mimic has a resemblance to another species, the model. • Types: • Batesian • Müllerian

Batesian Mimicry • Palatable species mimics an unpalatable model. Hawk moth larva Snake

Müllerian Mimicry • Two unpalatable species resemble each other. Cuckoo Bee Yellow Jacket

Competition • When two species rely on the same limiting resource. • Intraspecific competition usually more severe than Interspecific competition. • Why?

Competitive Exclusion Principle • Predicts that two species with the same exact requirement cannot co-exist in the same community. • The better adapted species will survive and the less adapted will go extinct.

Think, Pair, Share • Discuss if the Competitive Exclusion Principle explain the spacing of fast food restaurants on the “strip” in most towns.

Ecological Niche • The sum of a species’ use of the biotic and abiotic resources in its environment is called the species’ ecological niche. • How a species “makes its living” in its ecosystem. • Species can not have niche overlap, the Competitive Exclusion Principle

Niche Types 1. Fundamental - what a species is theoretically capable of using. 2. Realized - what a species can actually use.

Think, Pair, Share • Again in terms of fast food restaurants, explain the concept of a fundamental vs. realized niche.

Resource Partitioning • A way that species avoid niche overlap by splitting up the available resources. • Ex: Anolis lizards

A. distichus A. insolitus

Symbiosis • When two different species live together in direct contact. • Types: 1. Parasitism 2. Commensalism 3. Mutualism

Parasitism (+/-) • Parasite harms the host. • Parasites may be external or internal. • Well adapted parasites don't kill the host. • https: //www. youtube. com/watc h? v=uvdi. Yg 6 ZN-U Sci-Show Parasites

Commensalism (+/o) • One partner benefits while the other is unchanged. • Ex. – Cattle and Egrets

Mutualism (+/+) • Both partners Acacia Tree and Ants benefit from the interaction. • Ex: Pollinators and flowers

Species with large impacts • Some species have larger impacts on a community structure than others. • Ex: • Dominant Species • Keystone Species • Foundation Species

Dominant Species • A species that is the most abundant or has the highest biomass in a community. • Has a major effect on a community both biotically and abiotically.

Reason for Dominance? • Best Competitor? • Best in avoiding predators and disease? • Invasive species may fit the last explanation.

Example • Chestnuts – used to make up to 40% of the forest. • Lost between 1910 -1950 because of fungus disease. • Major impact on wood and nut industries.

Response • Some tree species increased in abundance to fill the gap. • Mammals and birds did OK. • 7 species of insects went extinct.

Keystone Species • Not a dominant species, but has a major impact in the community structure. • Often a top predator that controls the numbers of other species. • Ex. Sea Otters

Foundation Species • Species that cause physical changes in the environment that affect others. • Ex. Beavers, Bison, Black Rush

• https: //www. youtube. com/watc h? v=ysa 5 OBh. Xz-Q • How wolves change rivers

Succession • Changes in species composition over time.

Succession Stages • Climax Community - An ecological community in w hich populations of plants or animals remain stable and exist in balance with each other and their envi ronment.

Succession Types 1. Primary 2. Secondary

Primary Succession • Succession with only abiotic materials as the starting substrate • Ex: volcanic islands glaciated areas road cuts

Secondary Succession • Succession with biotic materials (living or dead) as the starting substrate • Ex: • Cutting down a forest • Forest fire • Tornado/storm damage

Steps of Succession • Pioneer Species – the first organisms to appear in the area in primary succession • Usually moss or lichens

What do Pioneer Species Change? • Enrich the soil – as generations die, their remains decompose and add nutrients to the soil (often N). • The soil is now able to support a greater variety of species such as grasses and small shrubs.

• Which occurs faster, primary or secondary succession? • What can you do to speed up succession?

Point • If you understand the causes and controlling factors of succession, you can manipulate them.

Some points about Succession • The Organisms are changing in the area over time. General pattern is an increase in biodiversity. • The Climate of the area is NOT changing over time.

Other Changes • Soil – becomes richer in N, more depth, better water retention etc. • Light – can decrease at ground level because of shading by taller plants.

Summary • Know the various types of interspecific interactions. • Know the Competitive Exclusion Principle and Niche Concept. • Know Species with large impacts.

Summary • Know some examples and causes of succession.