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Population in Ecosystems

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Biology

Ecology studies the relationships between organisms and their environment, including abiotic (non-living) and biotic (living) factors. Here, we discuss how organisms interact with their own species define keywords in ecology, such as populations and niches.

What is a population?

We probably think about the human population when we hear the word population. However, we can also have populations of dogs, cats, wolves - basically any species. This is because a population is defined as all the individual organisms found in a given habitat of one species.

Population: all the individual organisms found in a given habitat of one species.

What is a community?

A community is made up of all the various populations in a habitat. Species do not exist on their own; they interact with other species living in the same area to form communities.

Community: all the living populations in a given area.

A rainforest community might include several species of trees and shrubs growing at different heights and occupying different layers of the rainforest. It would also include the many birds, mammals, and insects who feed on these plants, as well as worms, fungi and bacteria that break down waste in the ecosystem.

What is an ecosystem?

So what is an ecosystem? An ecosystem includes the community of living organisms in a habitat and all the non-living (abiotic) components, such as water, soil and temperature. Ecosystems vary in size and scale. Some, such as ocean ecosystems, are extremely vast, while others, like pond ecosystems, are relatively small. Even humans can be considered ecosystems, as they are home to many complex interacting communities of microorganisms.

Ecosystem: the collection of all communities in a habitat, together with the abiotic components.

In a rainforest ecosystem, the plant community produces energy from the sun which is then consumed by the other organisms, and waste is recycled by other organisms in the system as well. In other words, the rainforest is a relatively self-sustaining unit. Little energy is exchanged between the rainforest and other ecosystems. However, no ecosystem is completely self-contained. For instance, many birds migrate between distant habitats at certain times of the year, thus linking multiple ecosystems.

Ecosystems are dynamic and this is because the biotic and abiotic components are constantly in flux. Biotic factors, such as competition, and abiotic factors, such as temperature, can change at any time. These changes can happen at different rates, with some occurring very quickly (e.g., a decrease in population size due to the spread of a disease) and others very slowly (e.g. rocks undergoing erosion over time).

Competition: where two organisms strive to obtain limited resource supplies. Intraspecific competition occurs between individuals of the same species whereas interspecific competition occurs between individuals of different species.

Population in ecosystem Example of an ecosystem StudySmarterFigure 1. Ecosystems. Source: Finty Royle - StudySmarter Originals

Two major processes are very important to consider within an ecosystem. This includes the flow of energy and the flow of nutrients.

Flow of energy

First, there is a constant flow of energy between the organisms in the ecosystem, which occurs through feeding. Producers, such as plants, are eaten by primary consumers, who are then eaten by secondary consumers, who are eaten by tertiary consumers. When organisms die, they are decomposed and recycled.

Producers: organisms that generate organic molecules, usually by photosynthesis.

Consumers eat other organisms to obtain their energy, including primary, secondary and tertiary consumers.

Flow of nutrients

The second important process is the constant flow of nutrients within the ecosystem. Nutrients such as carbon, nitrogen, phosphorus, and important molecules such as water are recycled within the ecosystem.

Carbon flows within the ecosystem in a process known as the carbon cycle. Carbon enters the atmosphere as carbon dioxide from the respiration of organisms, as well as emissions from factories, cities, and homes. It is then taken up by primary producers, who convert it into glucose during photosynthesis. Animals consume these plants and pass the energy along the food chain; they also continue to respire and release carbon as waste. Eventually, plants and animals die and decompose, and the carbon in their bodies returns to the atmosphere or is used as fuel.

Population in Ecosystems carbon cycle StudySmarter

Figure 3. Carbon cycle. Source: Finty Royle - StudySmarter Originals

What is a habitat?

Organisms live in habitats, which are areas characterised by their physical conditions and occupants. An ecosystem is composed of several habitats.

A rainforest ecosystem includes the canopy habitat, which might be home to some species of birds, as well as the forest floor habitat, which is home to fungi and small mammals. Habitats also house smaller units called microhabitats, which, as their name suggests, are home to organisms on an even smaller scale, such as worms and bacteria.

What is a niche?

In ecology, a niche describes the way that an organism fits into its environment. In other words, a niche is where the organism lives, what it does there, and how it interacts with others and its environment. It describes the organism’s role in the ecosystem.

According to the competitive exclusion principle, no two species occupy the same niche in the same habitat. This is the proposition that two species that use the same limited resource cannot coexist at constant population levels, as even the slightest advantage of one species over another will allow the dominant species to outcompete the other to the point of extinction or exclusion. In other words, complete competitors cannot coexist.

Population in Ecosystems - Key takeaways

  • A population is defined as all the organisms of a particular species in a given habitat. A community is defined as all of the populations that live together in a particular place at the same time.

  • A community is defined as all of the populations that live together in a particular place at the same time.

  • The two major processes to consider in an ecosystem are the constant flow of energy between organisms and the constant flow of nutrients in the ecosystem.

  • A niche describes the way that an organism fits into its environment. Due to the competitive exclusion principle, no two species can occupy the same niche.

Population in Ecosystems

Members of the same species that live and interbreed with one another in the same habitat comprise a population. 


Multiple populations of different species can exist and interact together as a community. An ecosystem is composed of one or more communities.

Ecosystems are dynamic. Many features within ecosystems, both biotic and abiotic, constantly undergo changes at many different rates. Populations are constantly changing, whether it’s in terms of their size or composition.

Competition describes when organisms compete for the same resources within an environment. These resources, such as food, water, shelter, light and territory, are required for survival and reproduction. Members of the same species may also compete for mates. Competition among members of different species is referred to as intraspecific competition, while competition among members of the same species is called interspecific competition.

An ecosystem is comprised of the many communities in a habitat and the abiotic factors present. 

Populations are composed of individual organisms in a given habitat of one species. 


This can include a population of humans, a population of whales, or a population of donkeys!

Final Population in Ecosystems Quiz

Question

An ecosystem is a system composed of one or more ________ of species that interact with one another and the _____ factors in the environment. 



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communities, abiotic



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Question

What are two important constant processes to consider in an ecosystem?

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Answer

The constant flow of energy and the constant flow of nutrients.



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What is a community?



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A community is defined as all of the populations that live together in a particular place at the same time.



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Why can’t two species exist together in the same niche?



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The competitive exclusion principle states that two species that use the same limited resource cannot coexist at constant population levels, as even the slightest advantage of one species over another will allow the dominant species to outcompete the other to the point of extinction or exclusion.



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What is the term for a reasonably well-defined place characterised by its physical conditions and occupants?



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Habitat



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A niche is an organism’s _____ in an ecosystem.



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Answer

role

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According to the competitive exclusion principle,  _______ competitors cannot coexist.


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Answer

Complete



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Are ecosystems large or small? 



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An ecosystem can be either large or small. An ocean is an example of a large ecosystem, while a pond is a small ecosystem.



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A community is made up of many species. True or false?



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True

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Describe the constant flow of energy process.



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Producers such as plants are eaten by primary consumers, who are then eaten by secondary consumers, who are eaten by tertiary consumers. When organisms die, they are decomposed and recycled.



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What is ecology?


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The study of the relationships between organisms and their environment, including abiotic and biotic factors.

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What is an ecosystem?

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Answer

A system composed of one or more communities of species that interact with one another and the abiotic factors in the environment.

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What is a community?

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Answer

Community refers to all of the populations that live together in a particular place at the same time.

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An ecosystem is composed of ______ habitats

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several

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Ecosystems are dynamic - true or false?

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True

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Question

Define succession.



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Answer

Succession refers to the changes in the species that occupy a particular area over time.



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Define primary succession.

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Answer

Primary succession occurs when a newly exposed or formed terrain is gradually colonised by new species.



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Which of the following traits is not likely to describe a pioneer species?


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Carnivorous



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Identify which stage of succession lichen is likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).



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Answer

Pioneer species

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Identify which stage of succession very large trees are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).



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Answer

Climax community



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Identify which stage of succession bryophytes are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).



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Secondary colonisers



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Identify which stage of succession shrubs are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).


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Shrubland

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Identify which stage of succession field mice are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).


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Tertiary colonisers

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Identify which stage of succession thermophylic bacteria are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).


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Answer

Pioneer species

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Identify which stage of succession mushrooms are likely to belong to (pioneer species, secondary colonisers, tertiary colonisers, shrubland, climax community).


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Answer

Tertiary colonisers 

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Question

True or false. Secondary succession usually occurs at a faster rate than primary succession.



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Answer

True

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Why does secondary succession occur faster than primary succession?


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Newly cleared environments still have some of the resources they were able to accumulate over many years of succession. Surrounding areas that were not cleared provide an influx of species.



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Which of the following is not a result of succession?

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Answer

The environment loses nutrients.

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Which of the following stages of succession has the highest species richness?



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Answer

Tertiary succession 

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Why are climax communities usually less diverse than intermediate communities?



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Answer

Because dominant species begin to outcompete and eliminate other species.



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 Competition arises when two or more individuals share a ______ resource.



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Answer

limited

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_________ competition occurs between individuals of the same species, while __________ competition occurs between individuals of different species.



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intraspecific, interspecific

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Which principle states the following: ‘Two species that use the same limited resource cannot coexist at constant population levels; the one that uses these resources most effectively will eliminate the other.’?



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Answer

The competitive exclusion principle



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Question

Which is not an example of a predator-prey relationship?

-        Praying mantis and spider

-        Owl and field mouse

-        Cow and grass

-        Hawk and eagle



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Answer

Hawk and eagle

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Predator-prey relationships follow a ______ pattern.



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cyclical

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Why might the effects of competition on population size be difficult to determine?



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Answer

There are many complex and interconnected factors that affect population size; causal links are difficult to establish in natural populations as there may be a time lag between the instance of competition and its effect on population size.



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Question

Determine whether the following scenario is best described by interspecific competition, intraspecific competition, or predation.


Praying mantises feed on small insects in their habitat.




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Answer

Predation

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Question

Determine whether the following scenario is best described by interspecific competition, intraspecific competition, or predation.


As the largest trees in the forest develop denser foliage, shrubs on the forest floor have less exposure to light.



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Interspecific competition

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Determine whether the following scenario is best described by interspecific competition, intraspecific competition, or predation.


Fur seals fight one another to claim territory along the coastline during mating season.



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Answer

Intraspecific competition

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Question

Determine whether the following scenario is best described by interspecific competition, intraspecific competition, or predation.


Squirrels are fond of eating all kinds of seeds.



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Answer

Predation



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Why aren’t prey eradicated by the predator?


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A wide range of external factors can allow the prey to survive. For instance, the area over which the prey population can disperse is usually much larger and more varied; this makes them harder to find and harder to catch. Predators may also have to contend with other factors such as competition with other potential predators, surviving the effects of heat or cold, and navigating difficult terrain, or they might even have to survive as prey themselves.



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What is predation?


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Predation is a process wherein one organism consumes another organism.

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What is competition?

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Competition arises when two or more individuals share a limited resource. 



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What are some examples of limited resources?

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Answer

  • Light
  • Water
  • Nutrients
  • Food

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Question

Define conservation

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Answer

Ways in which the environment, its inhabitants, and the resources it provides are preserved through protection and management.

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Give three examples of conservation.

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Any from:


  • National Parks
  • Marine Parks
  • Zoos
  • Frozen Zoos
  • Botanical gardens
  • Seed banks

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Why are national parks good?


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They are a conservation method that keeps a species in its natural habitat.

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Why is it good to keep a species in its natural habitat?

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It keeps them in an area where their natural support systems already exist

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What is an advantage of tourism to conservation?


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It increases money and awareness for the conservation effort.

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What is an endangered species?

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A species that is being threatened with extinction.

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