Daily Science Water (if needed) and measure height of pea plants Make a data table for 7 days on a notebook or notebook sheet of paper. Take your time, this will be turned in eventually for the lab!

Chapter 54 Community Ecology

Overview: A Sense of Community A biological community is an assemblage of populations of various species living close enough for potential interaction How many interactions are occurring here between species?

Concept 54.1: Community interactions are classified by whether they help, harm, or have no effect on the species involved Ecologists call relationships between species in a community interspecific interactions Examples are competition, predation, herbivory, and symbiosis (parasitism, mutualism, and commensalism) Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0)

Competitive Exclusion Interspecific competition (–/– interaction) occurs when species compete for a resource in short supply Strong competition can lead to competitive exclusion, local elimination of a competing species The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place

Ecological Niches The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche An ecological niche can also be thought of as an organism’s ecological role Ecologically similar species can coexist in a community if there are one or more significant differences in their niches

A. distichus perches on fence posts and other sunny surfaces. Fig. 54-2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii Figure 54.2 Resource partitioning among Dominican Republic lizards A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

The presence of one barnacle affects the distribution of another Fig. 54-3 EXPERIMENT High tide Chthamalus Chthamalus realized niche Balanus The presence of one barnacle affects the distribution of another One barnacle species is removed from niche Balanus realized niche Ocean Low tide RESULTS High tide Figure 54.3 Can a species’ niche be influenced by interspecific competition? Chthamalus fundamental niche Ocean Low tide

Predation Predation (+/– interaction) refers to interaction where one species, the predator, kills and eats the other, the prey What are some feeding adaptations that predators use for feeding and killing? Answer: claws, teeth, fangs, stingers, and poison

Prey display various defensive adaptations, can you think of some? Answer: hiding, fleeing, forming herds or schools, self-defense, and alarm calls Animals also have morphological and physiological defense adaptations Cryptic coloration, or camouflage, makes prey difficult to spot

Bee orchid (a) Cryptic coloration Canyon tree frog (b) Aposematic Fig. 54-5 (a) Cryptic coloration Canyon tree frog (b) Aposematic coloration Poison dart frog Bee orchid (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Figure 54.5 Examples of defensive coloration in animals (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Green parrot snake Yellow jacket

Herbivory Herbivory (+/– interaction) refers to an interaction in which an herbivore eats parts of a plant or alga It has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores

Concept 54.2: Dominant and keystone species exert strong controls on community structure In general, a few species in a community exert strong control on that community’s structure Two fundamental features of community structure are species diversity and feeding relationships

Species Diversity Species diversity of a community is the variety of organisms that make up the community It has two components: species richness and relative abundance Species richness is the total number of different species in the community Relative abundance is the proportion each species represents of the total individuals in the community

Which forest is more diverse? Fig. 54-9 Which forest is more diverse? A B C D Community 1 Community 2 Figure 54.9 Which forest is more diverse? A: 25% B: 25% C: 25% D: 25% A: 80% B: 5% C: 5% D: 10% Answer: Forest 1

Trophic Structure Trophic structure is the feeding relationships between organisms in a community It is a key factor in community dynamics Food chains link trophic levels from producers to top carnivores A food web is a branching food chain with complex trophic interactions

A terrestrial food chain A marine food chain Fig. 54-11 Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Figure 54.11 Examples of terrestrial and marine food chains Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

Species may play a role at more than one level Fig. 54-12 Humans Species may play a role at more than one level Smaller toothed whales Baleen whales Sperm whales Crab-eater seals Leopard seals Elephant seals Birds Fishes Squids Figure 54.12 An antarctic marine food web Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton