3-22-18 Populations & Communities Ch. 14, Lesson 2 Standards: SC.7.L.17.2, SC.7.L.17.3

Do Now: In your science notebook, state whether you agree or disagree with the following statements. Changes that occur in an ecosystem can cause populations to become larger or smaller. Some organisms have relationships with other types of organisms that help them to survive.

Populations & Communities Essential Questions How do individuals and groups of organisms interact? What are some examples of symbiotic relationships?

Vocabulary limiting factor biotic potential carrying capacity habitat niche symbiotic relationship

EQ: How do individuals and groups of organisms interact? SC.7.L.17.3 Objective: Students will be able to describe various limiting factors in an ecosystem and their impact on native populations.

Populations The area in which a population lives can be very large, such as the population of all the fish in the ocean, or very small, like fish in a lake. Population: all the members of one species that live in an area. Poblacion: todos los organismos de la misma especie que viven en la misma area al mismo tiempo.

Populations Ex: a parrot, a fallen tree, dead animals Biotic factors: all of the living or once- living things in an ecosystem. Abiotic factors: the nonliving parts of an ecosystem. Ex: a parrot, a fallen tree, dead animals Factor biotico: ser vivo a que una vez estuvo vivo en un ecosistema. Ex: Water, light, temperature, atmosphere, soil Factor abiotico: componente no vivo de un ecosistema.

Populations Sometimes the size of a population changes because the ecosystem changes. If either biotic or abiotic factors in an ecosystem change, a population can also change. Ex. If water temperature increases too high, fish can die. Ex. If the number of predators of fish increase, the fish population may decrease.

Populations Population density describes the number of organisms in the population relative to the amount of space available. Think about the hallways at SCA. Are they crowded or is there lots of room? The population density in the hallways reflects how crowded it is. High population density Low population density

Populations If a population is very dense, organisms might have a hard time finding enough resources to survive. Because there is not an infinite amount of space and resources, there is a limit to how large a population can get.

Limiting Factors Limiting factor: a factor that can limit the growth of a population. Factor limitante: factor que limita el crecimiento de una poblacion. The amount of available water, space, shelter, and food affects a population’s size.

What are the limiting factors shown? Identify the biotic limiting factors and abiotic limiting factors.

Limiting Factors Space to build homes Competition from growing population Presence of predators Limited amount of resources Death from disease

Populations Imagine a population of rabbits with a constant supply of food, an unlimited amount of land, and no predators. What would happen to the rabbit population? The population would keep growing until it reached its biotic potential: the potential growth of a population if it could grow in perfect conditions with no limiting factors. Potencial biotico: crecimiento potencial de una poblacion si puede crecer en condiciones perfectas sin factores limitantes.

Populations Almost no population reaches its biotic potential. Instead, it reaches its carrying capacity: the largest number of individuals of one species that an ecosystem can support over time. Capacidad de carga: numero mayor de individuos de una especie que un medioambiente puede mantener. The limiting factors of an area determine the area’s carrying capacity.

Populations Sometimes a population becomes larger than its carrying capacity. Overpopulation is when a population’s size grows beyond the ability of the area to support it. This often results in overcrowding, a lack of resources, and an unhealthy environment. For example, waste might build up faster than it is broken down, making the population sick.