Ecology is the study of the interconnections between living organisms and their environment. There is such a complex network of links in any location that ecologists have to break down and classify these relationships whether they be feeding, competition or reproduction. This topic is an introduction to these divisions.
Key concepts
Learn and test your biological vocabulary for 4.1 Species and communities using these flashcards
Essentials
These slides summarise the essential understanding and skills in this topic. They contain short explanations in text and images - good revision for all students.
Read the slides and look up any words or details you find difficult to understand.
Summary
Summary list for topic 4.1 Species and communities
Species are "groups of organisms that can potentially interbreed to produce fertile offspring".
Members of a species may be reproductively isolated in separate populations.
Species can be autotrophic or heterotrophic in nutrition (a few species are both).
Consumers are heterotrophs that feed on living organisms by ingestion.
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
A community is "populations of different species living together and interacting with each other."
An ecosystem is "a community and its interactions with the abiotic environment."
Autotrophs obtain inorganic nutrients from the abiotic environment.
The supply of inorganic nutrients is maintained by nutrient cycling.
Ecosystems have the potential to be sustainable over long periods of time
Skills (can you ....)
Classify species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
Set up sealed mesocosms to try to establish sustainability. (Practical 5) Mesocosms in sealed glass vessels are preferable because entry and exit of matter can be prevented but light can enter and heat can leave. Aquatic systems are likely to be more successful than terrestrial ones.
Test for association between two species using the chi-squared test with data obtained by quadrat sampling. For example An ecosystem chosen where varying factors affect the distribution of the chosen species. Random quadrat sampling should be used to measure the presence or absence of the chosen species.
Mindmaps
These diagram summaries cover the main sections of topic 4.1 Species and communities Study them and draw your own list or concept map from memory.
Exam style questions
This question requires knowledge of the different methods organisms use to gain energy.
Compare and contrast the sources of energy and organic nutrients of consumers, detritivores and saprotrophs. (4 marks)
Compare and contrast the sources of energy and organic nutrients of consumers, detritivores and saprotrophs. (4 marks)
Consumers get their energy from eating living organisms by ingestion but Detrivitivores ingest dead organisms, and decaying matter.
Detritivores obtain organic nutrients from decaying matter by internal digestion whereas saprotpophs obtain these things from dead organisms by external digestion.
All three types of nutrition are heterotrophic. They are all heterotrophs.
Heterotrophs need to obtain organic nutrients and energy from other living organisms because they cannot do photosynthesis.
Extra exam question on sustainability in ecosystems - - - Click the + to open it -- >
This question requires knowledge of sustainability in ecosystems. Answer the question below on paper and then check your answer with the model answer.
Question: Discuss the importance of sustainability in an ecosystem (6 marks)
Examiner hints- Discuss means offer a considered and balanced review that includes a range of arguments, factors or hypotheses. Opinions or conclusions should be presented clearly and supported by appropriate evidence.
In ecology responses, use scientific terminology precisely.
Click the + symbol to show the model answer
Model answer
Question: Discuss the importance of sustainability in an ecosystem (6 marks)
A sustainable ecosystem has a balance between all the components of the system/biotic and abiotic factors.
Biotic factors include producers, consumers, and recyclers.
Sustainability requires biodiversity as each member of the community needs to be in balance with the others.
Population size of the different levels in a food web need to be within sustainable levels, overpopulation of one level can imbalance other levels and affect the balance of the ecosystem.
There is a finite supply of nutrients for producers.
Nutrients must be recycled.
Abiotic factors include climate, rainfall, temperature.
Disturbance to the abiotic factors such as drought may reduce the ability of one or more species to survive.
Which can affect the biodiversity of the system necessary for the balance needed for sustainability.
Test yourself
This is a self marking quiz containing questions covering the topic outlined above. Try the questions to check your understanding.
Which classification grouping includes all organisms which have the potential to interbreed and produce fertile offspring?
Species are "groups of organisms that can potentially interbreed to produce fertile offspring".
When members of a species are separated by a physical barrier this can lead to populations which are prevented from reproducing, because individuals from each population never meet.
What is the name given to this situation?
Members of a species may be reproductively isolated in separate populations.
Which is the best definition of the term, "Heterotrophic"
Heterotrophs need to obtain organic material from other organisms. They cannot produce organic material from inorganic molecules.
Energy in an ecosystem is passed from organism to organism in food, but it is eventually lost to the environment as heat. Inorganic nutrients are not usually lost from the ecosystem?
What is the name given to the process which keeps the inorganic nutrients in the ecosystem?
Autotrophs obtain inorganic nutrients from the abiotic environment. Heterotrophs get nutrients by eating other organisms, but this is not the reason why the community is sustainable.
The supply of inorganic nutrients is maintained by nutrient cycling.
Ecosystems have the potential to be sustainable over long periods of time
The organisms in the photo below are classified in ecology according to their mode of nutrition.
Which of the following correctly describes their mode of nutrition?
Classifying species using their mode of nutrition begins with the division into Heterotrophs, who get organic molecules (nutrients) from other organisms and autotrophs, who can make organic molecules from inorganic molecules, using photosynthesis.
Mesocosms can be used by ecologists to investigate natural systems.
Which variables could be easily controlled in experiments using these aquatic mesocosms?
Mesocosms can allow the control of variables much more than the natural environment. These tanks are all the same size, so naturally volume, and surface area can be easily controlled. In setting up the tanks the concentration of salts can be accurately measured, as there is no movement of water through the tanks, this can also be controlled.
In an experiment in a small garden, quadrat frames were used to sample the flowers.
Why is it important to use random sampling in the placement of the quadrats?
Random quadrat sampling is a standard method used to avoid bias and selection.
What is the term given to a community and it's abiotic environment?
A community is "populations of different species living together and interacting with each other." An ecosystem is "a community and its interactions with the abiotic environment." A habitat usually relates to one species, and a biome is more than one ecosystem.
Drag and drop activities
Test your ability to construct biological explanations using the drag and drop questions below.
The components of an ecosystem and their interactions are an important part of this topic.
Drag and drop the correct word to define the components of an ecosytem.
A community is a naturally occurring group of inhabiting a particular environment and interacting with each other (for example by relationships), and relatively of other groups.
An ecosystem is a community of organisms and their environment.
The abiotic component of an ecosystem is the element of an ecosystem.
The component of an ecosystem is the community of an ecosystem.
Examiner hint: Use the correct terminology in responding to questions on ecology.
Click the '+' symbol to open the next explanation.
Extra drag and drop explanation on the biotic components of an ecosystem, click to open.
The biotic components of an ecosystem are the living organisms
Drag and drop the correct term into the gap to outline the feeding methods of the community in an ecosystem.
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Autotrophs (Primary producers) manufactures compounds from using energy. They are found at the trophic level, the basis of the food chain.
are consumers that feed on the organic compounds of living organisms by . They are found at levels of the food chain except the first.
Detritivores obtain organic nutrients from detritus by digestion.
Saprotrophs obtain organic nutrients from dead organisms by external digestion using of enzymes.
The ways in which organisms in an ecosystem obtain energy need to be understood.