Chapter 5by Tracy Reynolds

Rose, period 7

How do species interact?5 Major interactions

Interspecific competition- occurs when members of two or more species interact to gain access to the same limits resources such as food, light, or space.

Predation- occurs when a member of one species feeds directly on all or part of a member of another species.

Parasitism- occurs when one organisim feeds on the body of, or the energy used by, another organism, usually by living on or in the host.

Mutualism- an interaction that benefits both speciesby providing each other with food, shelter, or some other resource.

Commensalism- interaction the benefits one species but has little, if any, effect on the other

Competition for Resources

The most common intereaction between species is competition. Each species has its oen ecoligical niche. Some have broad nices, and some have narrow ones. When two species compete for the same reasouces such as food, the niches overlap. When overlapping, the competetion gets more intense. It’s very un common to find two spices sharing the same exact niche, and if the do, one species is always more dominant. Wich forces the other species to go extinct, change eating habits, or migrate to a new area.

Most Consumer Species feed on live organisms of other species

In predication, a member of one species (the predator) feeds directly on all or part of the living organism of another plact or animal species (the prey) as a part or a food web. Together, the two different species, such as lions and zebras, form a predator-prey relationship.

Most Consumer Species feed on live organisms of other species

Things such as herbivores, carnivores, and omnivores are predators, but technically not because they do not have to feed on live organisms. If you do prey on a live organisms, there are so many different ways the predators capture their prey. Things like camouflage, flying, speed (running), ambush, or even chemical warfare (venom).

Most Consumer Species feed on live organisms of other species

Even though the predators have advantages, so do the prey. Things like protective shells, speed, flying, and chemical warfare. An example is like a skunk letting off its stench to scare away the predator.

Predator and Prey species can drive each other evolution

When two different species interact for a long period of time, the gene pool can blend together and cause changes. Changes can help both sides become more competitive and reduce competition. They call this process, coevolution. Coevolution is like an arms race between interacting populations of different species. Sometimes predators, get the upper hand, then sometimes the prey does. It’s one of natures way of maintaining long-term sustainability through population control, and it can promote biodiversity by increasing species diversity.

Some Species feed off other species by living on or in them

This is parasitism, the parasite is usually smaller than the host. They gradually over time, draw nourishment for them from the host to gradually weaken them. Some also live inside the host, such as tape worms, or move move arond, like ticks.

Both species benefit

Mutualism, Both species provide each other with things like food and shelter. An example is the birds that ride on the back of large animals like buffalo and elephants, they eat the parasites and and pests off of them. They also make noise warning the larger animals when predators approach.

One species benefits, and other unharmed

Commensalism, an interaction that benefits but has has little or no effect on the other. An example, certain kinds of silver fish incests move alone with army ants to share the food, and the arms ants are unharmed, but have no benefit from it.

some species evolve to share resources

Some populations compete for the same resources and have to develop adaptation through natural selection. They do this to reduce competition, or you could say reducing niche overlapping. This happens through resource partitioning.

population dynamics

Populations differ in factors such as distribution, numbers, age structure and density. Population dynamics is specifically the study of how characteristics of populations change in response of change in the environment.

clumping

Animals live in clumps for:

protection

better resources

hunting in packs

mating

population growth, or shrinkage, or stability

Can change due to, births, deaths, immigration or emigration.

Emigration: departure of individuals from the population.

Immigration: arrival of individuals from outside population

population growth, or shrinkage, or stability

Population increase can cepende on the age structure, with is the amount you have of each age group. To young to reproduce, the once that can reproduce, and the ones to old to reproduce. Generally most population should have most of the age of the ones that can reproduce.

J-curve and s-curve

Species vary in biotic potential, or capacity for population growth under ideal conditions. populations with larger spices like elephants, have low biotic potential. The smaller species have high biotic potential.

J-curve and s-curve

instinct rate of increase: is the rate at which the population of a species would grow if it had unlimited resources.

environmental resistance: combination of all factors that act to limit the growth of all population.

carrying capacity: maximum population of a given species that a particular habitat can sustain indefinitely without being degraded.

J-curve and s-curve

A population with few, if any limitations in its resources can grow exponentially at a fixed rate such as 1% or 2% per year. Exponential or geometric growth starts slowly but then accelerates as the population increases, because the base size of the population is increasing. Plotting the number of individuals against time yields a J-shaped growth curve.

J-curve and s-curve

Logistic growth- involves rapid exponential population growth followed by a steady decrease in population growth until the population size levels off.

A plot of the number of individuals against time yields a sigmoid, or a S-shaped, logistic growth curve.

exceeding habitats carrying capacity can cause its population to crash

Some populations can over use all their resources and temporarily over-shoot. This occurs because of a reproductive time lag, period needed for the birth rate to fall and death rate to rise in response to resource overconsumption.

Different reproductive patters

Species capable for a high rate population increase are called r-selected species. Usually have many small offspring, and don’t show much parental activity. A lot of them die, so they can start the reproductive pattern again.

They can also be called opportunists, the reproduce repidly when conditions are favorable.

Different reproductive patters

Another one is called competitor or K-selected species. Reproduce later in life, very few off spring, and have lomg-term lives. They develop inside their mothers, come out fairly large, mature slow and are cared for by their parents.

Human population control

Things like bubonic plague, killed at least 25 millon people.

AIDS has also killed atleast 25 million people.

Ecological Succession

The gradual change in species composition in a given area.

Ecological Succession

Primary Succession: gradual establishment of biotic communities lifeless areas.

Secondary Succession: a series of communities with different species develop in places containing soil or sediment.

primary succession

Begins in a very lifeless area, or bottom sediment in aquatic system.

Usually takes awhile to start, but rock eventually starts to weather relasing nutrients.

Secondary Succession

Begins where an ecosystem has been disturbed, removed, or destroyed but some soil and bottom sediment remains. Things like cut down forest, or abandoned farmland.

succession has no specific path

According to traditional view, succession proceeds in an orderly sequence along an unexpected path until a certain stable type of climax community occupies an area.

Over the lasy several decades ecologist have changes their views about balance and equilibrium nature. The current view is that we cannot predict the course of a given succession or view it as preordained progress toward an ideally adapted climax plant community or ecosystem.

Living systems are sustained through constant change

It is useful to distinguish among two aspects of satiability in living systems. One is inertia, or persistence: the ability of a living system, such as grass land or forest, to survive moderate disturbances. A second factor is resilience: the ability of a living system be restored through secondary succession after a moderate disturbance.

However, there are limits to the stressed that ecosystems and global systems such as climate can take. As a result, such systems can reach a tipping pint, where any additional stress can cause the system to change in an abrupt and usually irreversible way that ofteninvolves collapse.