4.1 - 4.5 - The organisms in the environment Flashcards
What is a population?
A population is defined as a group of organisms of the same species living in the same place at the same time
What is a community?
A community includes all of the populations living in the same area at the same time
What is interdependence?
Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc
If one species is removed it can affect the whole community
What is a habitat?
A habitat is the place where an organism lives
What is an ecosystem?
An ecosystem is defined as all the biotic factors and all the abiotic factors that interact within an area at one time
What are biotics and abiotic factors?
The term ‘biotic factors’ includes all the living components such as plants and animals
The term ‘abiotic factors’ includes all the non-living components such as light intensity, mineral ions, water availability
Explain the Practical: Investigating Population Size?
One piece of equipment that might be used to investigate population size is a quadrat
Quadrats are square frames made of wood or wire
Plants species are commonly studied using quadrats to estimate the abundance
Quadrats do this by:
The number of an individual species: the total number of individuals of a single species (eg. buttercups) is recorded
Species richness: the total number of different species is recorded
Percentage cover: the approximate percentage of the quadrat area in which an individual species is found is recorded (this method is used when it is difficult to count individuals of the plant species being recorded eg. grass or moss
What are the results from this practical?
Once the results have been collected and the averages calculated, we can compare the abundance of the study species in each survey area
Species abundance is likely to be influenced by biotic factors such as:
Competition
Predator-prey relationships
Interactions with other organisms within the food chain or food web
The abundance will also be influenced by abiotic factors such as:
Light intensity
Mineral availability
Water availability
pH
Temperature
Salinity
What are the limitations of this experiment?
It can be easy to miss individual organisms when counting in a quadrat, especially if they are covered by a different species
Solution: Use a pencil or stick to carefully move leaves out of the way to check if there is anything else underneath
Identifying species may be tricky
Solution: Use a species key to identify the species
What is Biodiversity?
Biodiversity is the range and variety of different species of organisms on Earth, or within an ecosystem
It considers not only the species richness but the variation within each species, its distribution and population size
What is the importance of Biodiversity?
Food
Shelter (eg. birds nesting in trees)
Maintenance of the physical environment (eg. tree roots provide stability for soils, ensuring they do not get washed away. This in turn provides a stable habitat for other plant species)
High biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for these three things
Populations with high levels of diversity are also more likely to be resilient to sudden environmental impacts or disease
How is Biodiversity prevalent in the food web?
If the mouse population was suddenly wiped out, the fox and the hawk populations might decrease but would not be wiped out as mice are not their only food source
This example ecosystem has sufficient biodiversity to support the fox and hawk populations
The fox population can still depend on the rabbit and frog populations for food
The hawk population can still depend on the frog and sparrow populations for food
Explain the practical measuring biodiversity?
We can investigate biodiversity with quadrats using a similar method to the one used when investigating population size
2 tape measures
Quadrat
Random number generator
Species key
Method
Use 2 tape measures to lay out your first survey area
Use a random number generator to create a set of coordinates to place your first quadrat
Count the number of different species found within that quadrat
Repeat this process until you have collected the data for 10 quadrats
Repeat these steps for the second survey area
What are the results from measuring biodiversity?
The simplest indicator of biodiversity in this investigation is simply to compare the number of different species found in each survey area
A higher level of biodiversity would be indicated by a larger number of different species found in that area
However, this measurement of biodiversity is very simplistic as it doesn’t tell us about the distribution or population size in either survey area
As with species abundance, the biodiversity is likely to be influenced by biotic factors such as:
Competition
Predator-prey relationships
Interactions with other organisms within the food chain or food web
What factors can influence biodiversity?
Light intensity
Mineral availability
Water availability
pH
Temperature
Salinity
What are the abiotic factors affecting a community?
What are the biotic factors affecting a community?
