Interactions Within Ecosystems

Cast of Food Web Characters Tertiary Consumers – Animals that eat animals that eat animals Secondary Consumers – Animals that eat animals that eat plants Primary Consumers – Animals that eat plants Primary Producers – Plants and Phytoplankton: organisms using the sun for energy

Groups of living things interact within ecosystems The environment can be organized into five levels 1.Biome : region with similar climate, types of plants, and animals 2.Ecosystem: The living and non-living things that interact in one environment. 3.Community: The living organisms of an ecosystem 4.Population: A group of organisms of the same species that live in the same area. 5.Organism: A single living thing, made up of one or many cells, that is capable of growing and reproducing.

Patterns Exist in Populations Patterns in Living Space  Animals in a habitat are located based on food supplies, water, and shelter locations.  Some animals live in large groups for safety ( fish and elephants )

Patterns in Time  Population sizes can change with seasons  Many organisms migrate to other areas (monarch butterflies and birds)

Organisms Interact in Different Ways Organisms may cooperate, compete, or depend on each other for survival Predator and Prey relationships  Predators can affect how the prey populations are distributed (fish in large groups)  Prey can affect the location and number in predator populations (birds feeding on insects migrate to the areas where the insects are plentiful)

Organisms Interact in Different Ways Competition  Competition is the struggle between individuals or different populations for a limited resource

All the organisms in any ecosystem have some effect on every other organism in that ecosystem. Also any resource in any ecosystem exists only in a limited supply.  When these two conditions apply jointly, competition takes place.

Example: Seagull In a seagull colony on an oceanic outcrop, as the population grows, so the pressure for good nesting sites increases. This can affect the number of eggs that each female can successfully hatch, and so affects the birth rate of the population as a whole. This sort of interaction is called a Density Dependent factor - the effect is depends on the population density ( low density small effect, high density large effect). This mainly associated with pressure for food, nutrients or space.

 Competition can happen with the same species (plants compete for light, space, and nutrients)  Competition between different species (hyenas and vultures compete for remains of dead animals)

INTRASPECIFIC COMPETITION. Competition between members of the same species When the numbers of a population are small, there is little real competition between individuals for resources. Provided the numbers are not too small for individuals to find mates, population growth will be high. As the population grows, so does the competition between individuals for the same resources until eventually the carry capacity of the ecosystem is reached. In this situation, often the stronger individuals claim the larger share of the resources.

Intraspecific continued… Some species deal with intraspecific competition by being territorial. An individual or pair hold an area and fend off rivals. Individuals that are the most successful reproductively will hold the biggest territory and hence have access to more resources. Example: animals will often spray urine to mark their territories and claim their area

Intraspecific competition tends stabilize populations dependent upon the controlling resources.

Intraspecific produces something called logistic growth The graph illustrates this for a colony of yeast grown in a constant but limited supply of nutrient. During the first few days the colony grows slowly as it starts to multiply (lag phase) then it starts to grow very rapidly as the multiplying colony has a plentiful nutrient supply (exponential phase). Eventually the population size stabilizes as only a set number of yeast cells can exploit the limited resources (stationary phase). Anymore yeast cells and there is not enough food to go around.

INTERSPECIFIC COMPETITION Individuals of different species competing for the same resource. Interspecific competition may result in a balance, in which both species share the resource. The other outcome is that one species may totally out compete the other, this is the principal of competitive exclusion.

Interspecific Competition An example of both of these outcomes can be seen in a garden that has become overrun by weeds. A number of weed species coexist together, but often the original domestic plants have been totally excluded.

Interspecific Think of it like 2 species intersecting

In a woodland light is a limiting resource. Plant species that can not get enough light will die out in a woodland. This is especially true of small flowering plants on the woodland floor that are not only shaded out by trees but by shrubs and bushes as well. Beech trees have very closely overlapping leaves, resulting in an almost bare woodland floor.

But even in beech woods flowers manage to grow in the spring. Carpets of Snowdrops, Primroses and Bluebells an integral part of all Northern European deciduous woodlands in the spring. The key to these species success is that they grow, flower and reproduce before the shrub and tree species burst into leaf. They avoid competing directly with species that would out compete them for light by completing the stages of their yearly cycle that require the most energy and therefore the greatest photosynthesis when competition is less.

Organisms Interact in Different Ways Cooperation Some organisms work together to benefit each other  Killer whales hunt in pods (groups)  Ants, bees, and termites (members of a colony have different roles and responsibilities…queen bee, worker bees, etc.)

Survival of One Species Might Depend on Another Species Symbiosis: two different species who live together in a close relationship  Both species benefit  One species benefits while the other is not affected  One species benefits while the other is harmed

Types of Symbiosis Mutualism: Two species interacting with each other that benefits both species. (bees and flowers)

Types of Symbiosis Commensalism: two species interacting with each other with one species benefiting and the other unaffected. (jellyfish and fish)

Types of Symbiosis Parasitism: two species interacting while one species benefits and the host species is harmed Examples of human parasites.

Populations Change Over Time Population growth and decline  Predator-prey interactions can affect population increase or decrease ( as a wolf population increases the moose population decreases)  Birth rate may decline or increase

Populations Change Over Time  Limiting factors: any factor or condition that limits the growth of a population in an ecosystem (food, water, light, large group of predators, small group of prey)

Maintaining a Balance in an Ecosystem Carrying Capacity: the maximum number of individuals that an ecosystem can support. Limiting factors affect the carrying capacity

Main Points on Organism Interactions in Ecosystems Groups of living things interact within ecosystems (biome, ecosystem, community, population, organism) Organisms can interact in different ways (symbiosis: mutualism, commensalism, parasitism)

Bioaccumulation = the accumulation of a contaminant or toxin in or on an organism from all sources (e.g., food, water, air). An increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.

Biomagnification = the increase in concentration of toxin as it passes through successive levels of the food web

Ospreys and eagles are tertiary consumers and this makes them particularly vulnerable to DDT because of bioaccumulation and biomagnification.