Chapter 17 Biological Communities Coach Fults

Interaction Among Species Some interactions among species are the result of a long evolutionary history in which many of the participants adjust to one another over time Adaptations and natural selection led to relationships that help each other Coevolution- back-and-forth adjustments between interacting members of an ecosystem

Predators and Prey Coevolve Predation- act of 1 organism killing another for food Parasitism- 1 organism feeds on and usually lives on or in another Parasites usually don’t kill their host; host is used to transport offspring to another host

Face of Predation

Plant defenses against Herbivores Thorns or spines usually Most contain chemical compounds that discourage feeders Secondary compounds- defensive chemicals These chemicals are usually toxic to insects Ex: Cabbage butterflies’ larvae are able to feed despite of the mustard oils that are secreted

Symbiotic Species Symbiosis- 2 or more species live together in a close, long-term association These can be beneficial for both species but neither are harmed Mutualism- both species benefit Commensalism- one benefits and the other is unharmed

Common use of scarce resources and competition 2 species use the same resources it is referred to as competition They interact when abundance of resources is limited Compete for food,land,mates,shelter To understand how competition shapes an ecosystem you have to know what organisms do on a day-to-day basis

Common use of scarce resources and competition The functional role of a particular species in an ecosystem is called its niche; its “job” Niche is not its habitat Niches often affect the flow of energy throughout the ecosystem

Size of a species niche Fundamental niche- entire range of resource opportunities an organism is potentially able to occupy within an ecosystem Realized niche- actual range the species utilize

Competition The species that uses the resources the best will eventually win the battle Competitive exclusion- elimination of a competing species Competitors can coexist when their realized niches don’t overlap too much

Competitive exclusion

Biodiversity Because predation can reduce competition, it can also increase biodiversity, the variety of living things present in a community It is the measure of both the number of different species in a community (species richness) and the relative numbers of each of the species (species diversity)

Climate effect on where species live If you drove all over the world do- would you see the same organisms everywhere? Why? Climate- refers to the weather conditions in an given area

Temperature and Moisture 2 most important elements of climates Temperature and water availability will only allow certain species to survive

Major Biological Communities You will notice that species will live in similar climates all over the earth Biome- a major biological community that occurs over a large area

Terrestrial Biomes Tropical Rainforest- rain 80 to 180inches/year; most biodiverse; most nutrients are held in plants- the soil is not very fertile Savannas- 35 to 60 in/yr; grasslands; found in tropical areas; great temperatures differences; widely spaced trees; large animals roam

Terrestrial Biomes Taiga- cold-wet climate; coniferous trees; winters are long and cold Tundra- between taiga and permanent ice surrounding the north pole; 10in/yr; frozen ice is usually within 3 feet of the surface

Terrestrial Biomes in Texas Deserts Temperate grasslands Temperate Deciduous Forests (we live here) Temperate Evergreen Forests

Freshwater Communities Ponds and lakes have 3 zones Littoral zone- closes to shore Limnetic zone- open water near surface but away from shore Profundal zone- deep water; below where light can reach

Wetlands 2 nd in diversity to tropical rainforests Marshes and swamps Water soaked majority of the year Help in reducing flooding

Marine Most fish live in shallow waters near the coastlines where nutrients run off the land Plankton live on ocean’s surface; algae,bacteria,fish larvae,small invertebrates In the deep ocean, light does not reach; organisms have adapted to live without sunlight