INTERACTIONS IN THE ECOSYSTEM CHAPTER 5

Habitats and Niches Every organism is adapted to life in the habitat or ecosystem in which it lives The role of an organism in the ecosystem is called its niche (pronounced neesh) Niche made up of: abitoic factors: sunlight, temperature, water biotic factors: food source, position in the food chain, etc

More About Niches Competitive Exclusion - the extinction of a species due to direct competition for the same resources. The species that is better at getting the resources will force the other species to leave, change their niche or die Niche diversity is determined by the abitotic factors in a habitat

Predator/Prey A predator is an organism that hunts other organisms for food (prey) Predators can be a limiting factor in niche diversity Keystone Predator - A predator that causes a large increase in habitat diversity (Ex: a seastar in a tidepool

Evolution and Adaptation Ecosystems change over time All species adapt to niches in their environment The way many populations respond to environmental changes is by evolving or changing in response to changes in their environment.

Evolution and Adaptation Evolution is defined as a change in a population of organisms over time Organisms have three options in response to changes in the environment: adapting to different niches in the same habitat to avoid competing for the same resources move to a new habitat to avoid competition die (and possible extinction)

Convergent Evolution Similar ecosystems often have similar niches. Organisms from both ecosystems will also have similar adaptations Ex: Wings on a bee, a bird and a bat. The insect wing, bird wing and mammal wing all serve the same purpose but are very different on each organism. Sharks (fish) and dolphins (mammals) look similar, both have fins, but their bodies are very different in structure.

Coevolution Species that are dependant on and adapt to suit each other Monarch caterpillar eats only poisonous milkweed leaves – which make the adult butterfly poisonous to its predators. Acacia tree and ants - the trees have sharp thorns - provide ants with both food and a place to build their nests. Ants keep otherinsect pests away from the trees.

Populations The size of the population of any organism is dependent on the abiotic and biotic factors that shape each niche. Population size changes as the conditions in the niche change. Thomas Malthus (1798) studied human populations Charles Darwin (1859) studied plant and animal populations

Populations Exponential Growth – the growth rate of each generation is a multiple of the parent generation Plants: corn, rice, wheat, oak trees Animals: like sea turtles, alligators, mice, spiders, goldfish, robins, dogs and cats All have many babies – not all babies survive to become adults.

Growth Rate Darwin – noticed that most organisms produce many more offspring than will Actually survive into adulthood (some babies do die) Abiotic factors like water and land (space) limit population size and reproduction rate

Population Size Carrying Capacity – The number of individuals in any species that can be successfully supported by their ecosystem. Ex: The number of lynx that survive the Arctic winter depends on the number of snowshoe hare that available to eat. Black bears in NJ have exceeded the carrying capacity of the forest

Populations Limiting Factors – The forces that slow the growth in any population Density-Dependent factors: predators, food, disease Density-Independent factors: water, climate, living space, natural disasters, human disturbance

Limiting Factors Elephants are limited in population growth because the resources like water, food and land are limited in their African savanna habitat. There is a long dry season (with no rain) followed by a shorter rainy season. Elephants eat many tons of plants each day and need a lot water to drink and cool themselves with. Only one female in each family has a baby – the rest of the females help care for the young

CHAPTER 5 VOCABULARY (You Should Know) Niche Limiting factor Keystone Predator Prey Evolution Extinction Convergent evolution Adaptation Coevolution Evolve Exponential Growth Habitat Carrying Capacity Ecosystem Competitive Exclusion Migration