Ch 4 Ecosystems and Communities 4.2 Niches and Community Interactions
The Niche The conditions in which an organisms lives, and how it interacts with its environment (in the trees, on the ground, inside another organism) The role an organism plays in the environment (its job consumer, producer, predator, prey)
Includes: Its available resources (food, shelter, water) Physical aspects (the abiotic factors temperature, sunlight) Biological aspects (the biotic factors its reproduction, how it eats) Habitat the place an organism lives
Describing niches
Interactions Between Organisms Organisms within a community interact and can affect the size and characteristics of each other s population
Interactions are tightly interconnected, and each population depends on the other A change in one species population can affect the population of another species Increase/decrease in size Changes in behavior, characteristics, etc.
Keystone species species in a community that plays a vital role, and will have great impact if their population changes If they are a primary food source, primary predator, etc.
Competition Interaction in which two or more organism attempt to use the same limited resource (food, water, shelter) Interspecific comp. - Exists between species Gazelles and antelope eating same grass Intraspecific comp. - Exists within a species Gazelles in a population eating the same grass
Organisms try to limit competition, and will develop ways to share Species may specialize to eat at specific times or day, or in certain location Several species of warblers (small birds) avoid competition within the same tree by feeding at different levels (Figure 4.7 pg 101)
Competition in the meadow
Predation Interaction in which one animal kills and feeds on another animal Predator killer Prey Food Prey develops ways to avoid becoming food (camouflage, speed) but predator will develop in response to be better able to catch prey (better eyesight, faster speed/endurance)
Predator-prey cycles
Herbivory Interaction in which an animal (herbivore) feeds on plants Plants develop ways to avoid being eaten (poison, thorns) but animals also develop ways to get around them (immunity to poison, thick lips to avoid thorns)
Symbiosis Interaction in which species living in very close relation with each other Symbiosis
Mutualism Interaction in which both species involve are benefitted Sea anemone and clown fish Anemone provides protection for fish, fish protect anemone by chasing off other fish Fish
Commensalism Interaction in which one species benefits but the other is not affected Barnacles on a whale Barnacles need moving water to feed, whales are not affected by them
Parasitism Interaction in which one species benefits by the other is harmed Parasite organism that feeds and lives in/on another (tapeworm, flea, plasmodium) Host organism on which the parasite feeds harmed but does not immediately die. Why? Parasitic Wasps
Mutualistic and parasitic relationships
4.3 Succession
Ecological Succession The change in the composition of an ecosystem, usually the result of a disturbance (extinction, natural disaster or event, human impact)
Primary Succession Development of an ecosystem in an area that has never been occupied, or was completely destroyed Movement of organisms to an uninhabited island, or new land formed by volcanoes Pioneer species species that first inhabit an area
Secondary succession Change in the make up of a community found in an ecosystem that still contains some aspects of the previous community New populations of species come in and repopulate the area May develop in same way as original ecosystem, or change
Can follow a fire, hurricane, human impact (abandoning an empty lot, area left by logging or farming) Occurs faster than primary succession because some components (like soil) are already present
Climax communities After succession begins, the community of organisms may gradually change over time The stable community of organisms that eventually develops is called the climax community
Sand dune succession
Species adaptations during succession
From pioneer to climax community