Ch. 17 Biological Communities (pg. 361)

How Organisms Interact in Communities

Evolution in Communities

Interaction Among Species

Coevolution – the process in which long-term, interdependent changes take place in 2 species as a result of their interactions

Example: flowers and their pollinators

Predators and Prey Coevolve

Predation – an interaction between 2 species in which one species, the predator, feeds on the other species, the prey

Parasitism – a relationship between 2 species in which one, the parasite, benefits from the other species, the host, and usually harms the host

Plant Defenses Against Herbivores

Primary Defense – thorns, spines

Secondary compounds – Defensive compounds in plants

Ex.Make the plant taste badToxic compounds

How Herbivores Overcome Plant Defenses

Many herbivores have the ability to breakdown the secondary compounds – produce enzymes

Ex. Cabbage butterfly larva breakdown mustard oils that are toxic to most other insects

Monarch butterflies and milkweed

Symbiotic Species

Symbiosis – a relationship in which different organisms live in close association with each other

3 kinds of symbiotic relationships:

Mutualism

Commensalism

Parasitism

Mutualism – a relationship between 2 species in which BOTH species benefit

Flower and pollinator

Coral and photosynthetic algaeAnt and “milking” an aphid

A remarkable 3-way mutualism appears to have evolved between an ant, a butterfly caterpillar, and an acacia in the American southwest. The caterpillars have nectar organs which the ants drink from, and the acacia tolerates the feeding caterpillars. The ants appear to provide some protection for both plant and caterpillar.

© Gregory G. and Mary Beth Dimijian

Ant and acacia

The ant hollows out the large thorns of the plant for nests, feed on sweet secretions from the base of each petiole

Ants in return protect these trees from invertebrate as well as vertebrate herbivores. With any movement of the branch, the ants emerge releasing a nasty odor as well as physically attacking the surprised herbivore.

Commensalism – a relationship between 2 organisms in which one benefits and the other is unaffected

Whale with barnacles

Shark with pilot fish

Clownfish and sea anemone

Parasitism– a relationship between 2 species in which one, the parasite, benefits from the other species, the host, and usually harms the host

Tapeworm in carp

Tick feeds on blood of hostTapeworm

Competition – a relationship between species that attempt to use the same limited resource

How Competition Shapes Communites (pg. 365)

Common Use of Scarce Resources and Competition

Niche – the position (way of life) of a species in an ecosystem in terms of the physical characteristics (such as size, location, temperature, pH, etc) of the area where a species lives AND the function of the species in the biological community (position in food web, when it breeds, etc.)

No two species can occupy the exact same niche at the same time

Fundamental niche – the largest ecological niche where an organism or species can live without competition

(Realized niche – the range of resources that a species uses, the conditions that the species can tolerate and the functional roles that the species plays as a result of competition in the species fundamental niche)