T7 - organisation of an ecosystem Flashcards
What do food chains show?
Food chains show feeding relationships within communities, specifically the transfer of energy between trophic levels.
Define the term producer.
A producer is an organism that can produce its own carbon compounds, e.g. glucose, by chemical processes such as photosynthesis.
Describe the purpose of the investigation shown in the image below.
Diagram of a hillside showing the effect of altitude on growth of buttercups. Quadrats are placed along a transect line from 70m to 0m to measure buttercup frequency. The investigation shown will determine the effect of altitude on the distribution of buttercups on a hillside.
Define the term primary consumer.
A primary consumer is an organism that eats producers. Primary consumers are also known as herbivores.
Identify the primary consumer in this food chain.
Diagram showing the food chain: Sun providing energy to grass, which is eaten by a mouse, and the mouse is eaten by an owl, demonstrating energy transfer. The primary consumer in this food chain is the mouse, as it is eating grass, which is the producer.
Define the term secondary consumer.
A secondary consumer is an organism that eats primary consumers.
True or False? Herbivores are secondary consumers.
False. Herbivores are primary consumers. Secondary consumers eat primary consumers, making them carnivores.
Define the term tertiary consumer.
Tertiary consumers are organisms that feed on secondary consumers. They are carnivores and are present at the fourth trophic level of food chains.
True or False? In a stable community the numbers of predators and prey rise and fall in cycles.
True. In a stable community the numbers of predators will rise when prey numbers are high, then as prey numbers decline the predator numbers will also decline.
What is a quadrat?
A quadrat is a square frame that is placed on the ground to study the organisms within.
Define the term abundance in the context of a quadrat investigation.
The term abundance is how common a species is within a quadrat. Abundance across a series of quadrats can be used to estimate the size of a population.
How can the abundance of a species be measured within a quadrat?
The abundance of a species can be measured within a quadrat as follows: Recording whether or not a species is present, Counting the number of individuals of a species, Estimating percentage cover.
When might percentage cover be used as a measure of abundance within a quadrat?
Percentage cover is often used to measure the abundance of a species where individual organisms are difficult to tell apart, e.g. grass or barnacles.
Why is it important to place quadrats randomly when studying population size?
Placing quadrats randomly avoids bias in an investigation, e.g. a student might choose to place all of their quadrats on bare ground because it would make counting easier, resulting in a biased sample.
When using quadrats to compare population sizes in two areas, what variables should be kept the same?
Variables that should be kept the same when using quadrats to compare the populations of a species in two areas include: Size of quadrat, Number of quadrats sampled, Time of day / time of year, Knowledge of species identification.
What are some of the challenges of studying populations using quadrats?
Challenges of using quadrats to investigate populations include: It can be easy to miss organisms when counting, e.g. if they are underneath another organism or if two individuals are counted as one, Some species might be difficult to identify.
True or False? Increasing the number of quadrats will increase the likelihood that any results accurately represent the habitat sampled.
True. Carrying out more quadrats will increase the sample size, meaning that the results are more likely to be a good representation of the area sampled.
