Interactions in the Ecosystem CHAPTER 5 Interactions in the Ecosystem

Section 3.3 - The Ecosystem

Section 3.3 - The Ecosystem Levels of Organization Individual – one organism from a species. Species – a group of organisms so similar to one another that they can breed and produce fertile offspring. Since they all have the same needs they compete with one another for food, shelter, space, mates, etc. Populations – All the members of a species that live in the same geographic area, a group of the same species. Communities – are made up of different populations of organisms that interact in the same area at the same time. Ecosystems – are large places where all the biotic factors and abiotic factors interact with one another. Abiotic factors generally cause environmental differences. Biome – made up of ecosystems: grasslands, savannah, desert.

Section 5.1 – Habitats and Niches Habitat – the specific environment in which a particular species lives. Within their habitat individual organisms find the appropriate food, shelter, temperature and other factors needed to survive. Niche – the role or actions of an organism in an ecosystem; what the organism does in its habitat. An organisms niche is defined by all the biotic and abiotic factors in the environment. Competition occurs between species when they try to share the same niche.

Section 5.1 – Habitats and Niches Competitive Exclusion – the extinction of a population due to direct competition with another species for a resource in the same area. Not the extinction of the whole species! The presence of one species might limit the niche of another. Fundamental niche – a theoretical niche of an organism. The realized niche of an organism is an organisms actual niche.

Section 5.1 – Habitats and Niches Predator vs. Prey Predator – an organism that actively hunts other organisms. Prey – the organism that is hunted. Predator vs. prey relationships help keep environments stable.

Section 5.1 – Habitats and Niches Keystone predator – a predator that promotes a great niche diversity in its habitat. It increases the biodiversity in a habitat. If they are removed from an environment; it often decreases the overall diversity of organisms because a chain reaction of events will occur.

Section 5.2 – Evolution and Adaptation Ecosystems change over time Change in an environment will affect the niches of organisms. Changes in the environment affect the evolution of populations Evolution – a change in the characteristics of a population of organisms over time. Evolution happens when some individuals have genetic variations that allow them to produce more offspring with a certain trait or gene that is more advantageous for survival. “Survival of the Fittest” TIME

Section 5.2 – Evolution and Adaptation Evolving in a niche Specialized species – an organism with a small niche. Koala and eucalyptus trees. Pandas and bamboo. Vulnerable to extinction. Are less able to tolerate habitat disturbance, so would thrive in an area with outside human activity. Living on an island without human involvement.

Section 5.2 – Evolution and Adaptation Convergent Evolution If niches in two ecosystems are similar, the organisms that evolve there may also look alike. It is the independent development of similar adaptations (traits) in two species with similar niches. Wings of birds and wings of bats (mammals) because both their niches require flight.

Section 5.2 – Evolution and Adaptation Coevolution Organisms that live closely together and interact may have evolutionary responses to one another. Coevolution – species that interact closely may become adapted to one another through this process. Clown fish and sea anemone. Acacia (uh-kay-sha) tree and stinging ants.

Section 5.3 - Populations Population Growth Populations can quickly grow past the environment’s ability to support it. As a result of growing populations, organisms experience increased competition for resources. So populations can continually grow exponentially unless prevented by limited resources.

Section 5.3 - Populations Carrying Capacity As a population grows it takes move from its habitat and resources become scarce. The death rate rises because those who cannot compete die and the birth rate starts decreasing. The growth of the population slows down. The population will stop growing altogether because the number of births equal the number of deaths. Carrying capacity – the number of individuals of a species that can be supported by an ecosystem for a species. The carrying capacity for a species is usually determined by the ecosystem’s resources.

Section 5.3 - Populations Carrying Capacity The S-shaped curve represents the change in the size of a new population over time. The population starts out small and then increases rapidly. As the size of the population approaches carrying capacity, the growth rate slows down. The population stops growing when it reaches the carrying capacity and levels off.

Section 5.3 - Populations Limiting Factors Limiting factors – the force that slow the growth of a population. Human Disturbance Density- dependent Density Independent Climate Natural Disasters Water Availability Predation Population Size Living Space Parasitism Disease Food Competition

Section 5.3 - Populations Limiting Factors 2 Kinds 1. Density-dependent limiting factors – limiting factors that are dependent on population size. - Examples include: food supply, predation, and disease. - Are related to competition and other interactions between organisms. - Usually when one population declines, another population also declines. 2. Density-independent limiting factors – a limiting factor that affects the same percentage of a population regardless of its size. - Examples include: Natural disasters, climate and human disturbance.