Читать реферат по английскому: "Ecology Essay Research Paper In the original" Страница 1

(Назад) (Cкачать работу)

Ecology Essay, Research Paper

In the original Greek "oikos" means,

"house". So ecology is "the study of the house" the

place where you live, or the environment which

technically includes all those factors, both nonliving

and living, that affect an organism. Ecology then is

the study of the interactions of organisms in their

environment includes both the living (biotic) and

physical (abiotic) factors of the environment. It’s

also the science, which formulates and tests

hypotheses about environment. Ecology is the

relationships, identification and analysis of

problems common to all areas. Ecology studies

the population and the community, evaluates cause

and effects of the responses of populations and

communities to environmental change.

POPULATIONS The population is defined as an

assemblage of individuals of a single species that

live in the same place at the same time. Also,

biologists add an additional condition: the

individuals in a population must interact with each

other to the point of being able to interbreed.

Population is important to understanding many

important ecological and evolutionary phenomena.

Ecologists can use information from population

ecology to predict the success of a given species

or assemblage of species. One attribute of

populations that is observed in nature is their

dispersion, or the way in which individuals are

distributed in a given area. Typically, biologists

refer to three types of dispersion: – Clustered

(aggregated), Regular (evenly spaced), Random

(irregularly spaced) Populations showing a

clustered pattern are common in nature and are

found among many different types of organisms.

Clustered dispersion patterns are often due to

environment heterogeneity. Regular dispersion

patterns are relatively rare in nature and occur

when a resource is scarce. A good example of

regular spacing occurs in animals that exhibit

territoriality, a phenomenon in which animals

establish an area for themselves and fight off all

other individual seeking to invade that area.

Regular dispersion patterns can also be observed

in plants. Random patterns can be found in a

variety of organisms (trout in lake or maple trees in

a forest). Regardless of which organisms, the

number of births almost always has the potential to

be greater than the number of deaths. In other

words populations of all species have the capacity

to grow. That property is crucial importance to the

success of all species. However, all species will

not increase under all circumstance, but instead

they can, given appropriate conditions. There are

two models of population growth: the exponential

model and the logistic model. One of the most

basic models of population biology is the

exponential growth equation, which is: )N/)t =

rmaxN This equation states that, in a growing

population, the rate of change in population size is

determined by the maximal intrinsic rate of

increase (rmax) multiplied by the number of

individuals in that population (N). If a population

growth very quickly we called that an exponential

increase and its growth curve has a J-chaped

called J-chaped curve. A population cannot

continue to grow indefinitely because this equation

contains additional term called the carrying

capacity (K) which is not fixed, but carrying

capacity is constantly affected by many factors,

both biotic (living) and abiotic (non-living). The

logistic population growth predicts that

populations will grow rapidly at first. However, as

the number of individuals in the population (N)

approaches the carrying capacity (K), the

population growth rate eventually slows to zero,

and the population stabilize at K. The result is a

sigmoidal or S-shaped curve which is often

divided into three phases: the first is called the lag

phase (the period of slow growth that occurs

when population numbers are low). The second is

the log phase, which occurs when growth rate

accelerates and becomes relatively rapid. The

third is the saturation phase, during which

population growth decelerates as N approaches

K. All species have a well-defined life history that

involves a beginning of life, a juvenile and

reproductive phase and death. There are two

important parameters of a population: survivorship

(how long one live) and fecundity (how many

offspring one leaves). Survivorship is the number

still living at the beginning of each age interval. The

number of deaths determines the death rate during

a given period of time divided by the number still

living at the beginning of the time period.

COMMUNITIES A community is an assemblage

of populations that interact with one another and

the effects that they have on each other often

greatly influence their ability to survive and

reproduce. Because they are assemblages of

different species, communities have properties that

make them unique from individual organisms and

populations. Some communities simply blend

gradually into others and for this reason are called

open comments, forest communities are like that,

as different vegetable types blend together.

Похожие работы