chapter 11 p1 Flashcards
biodiversity
the variety of living organisms present in an area.
Biodiversity includes plants, animals, fungi, and other living things.
The importance of biodiversity:
Biodiversity is essential in maintaining a balanced ecosystem for all organisms.
All species are interconnected - they depend on one another.
For example, trees provide homes for animals.
Animals eat plants, which in turn need fertile soil to grow.
Fungi and other microorganisms help decompose dead plants and animals, returning nutrients to the soil.
In regions of reduced biodiversity, these connections may not all be present, which eventually harms all species in the ecosystem.
We rely on balanced ecosystems as they provide us with the food, oxygen and other materials we need to survive.
Unfortunately, many human activities, such as farming and clearing land for housing, can lead to a reduction in biodiversity.
Measuring biodiversity
Tropical, moist regions (that are warm all year round) have the most biodiversity.
The UK’s temperate climate (warm summers and cold winters) has less biodiversity.
Very cold areas such as the Arctic, or very dry areas such as deserts, have the least biodiversity.
Generally, the closer a region is to the Equator (the line of latitude of the Earth, halfway between the North Pole and South Pole), the greater the biodiversity.
For example, over 40000 plant species live in the Amazon rainforest, whereas less than 3000 live in Northern Canada.
How does Measuring biodiversity plays an important role in conservation:
It informs scientists of the species that are present, thus providing a baseline for the level of biodiversity in an area.
From this information, the effect of any changes to an environment can be measured.
These may include the effect of human activity, disease or climate change, for example.
Before a major project is undertaken, such as building a new road or the creation of a new nature reserve, an Environmental Impact Assessment (EIA) is undertaken.
This assessment attempts to predict the positive and negative effects of a project on the biodiversity in that area.
Biodiversity can be studied at different levels:
habitat biodiversity
Species biodiversity
genetic biodiversity.
Habitat biodiversity:
Habitat biodiversity refers to the number of different habitats found within an area. Each habitat can support a number of different species.
Therefore in general, the greater the habitat biodiversity, the greater the species biodiversity will be within that area.
The UK is home to large number of habitat types, including meadow, woodland, streams, and sand dunes. It has a large habitat biodiversity.
By contrast Antarctica, covered almost entirely by an ice sheet, has a very low habitat biodiversity and very few species live in this region.
On a smaller scale, countryside that is habitat rich, perhaps with a river, woodland, hedgerows and wild grassland, will be more species rich than farmed countryside with large ploughed fields making up a single uniform habitat.
Species biodiversity:
Species biodiversity has two different components:
species richness
species evenness
Therefore an area can differ in its species biodiversity even if it has the same number of species.
For example, a cornfield and a grass meadow may both contain 20 species.
However, in the cornfield, corn will make up 95% of the community with the remaining 5% made up of other organisms including weed plants, insects, mice, and birds.
In the grass meadow the species will be more balanced in their populations.
species richness
the number of different species living in a particular area,
species evenness
a comparison of the numbers of individuals of each species living in a community. (The community is all the populations of living organisms in a particular habitat.)
Genetic biodiversity:
Genetic biodiversity refers to the variety of genes that make up a species. Humans have about 25000 genes, but some species of flowering plants have as many as 400000 genes.
Many of these genes are the same for all individuals within a species. However, for many genes, different versions (alleles) exist.
This leads to genetic biodiversity within a species
Genetic biodiversity within a species can lead to quite different characteristics being exhibited.
For example, some genes are the same for all breeds of dog - these genes define the organism as a dog.
Some of the genes have many alleles - they code for the wide variation in characteristics seen between different breeds of dog. for example coat colour and length.
Greater genetic biodiversity within a species allows for better adaptation to a changing environment, and is more likely to result in individuals who are resistant to disease.
What is sampling:
- taking measurements of a limited number of individual organisms present in a particular area.
- Sampling can be used to estimate the number of organisms in an area without having to count them all.
- The number of individuals of a species present in an area is known as the abundance of the organism.
- Sampling can also be used to measure a particular characteristic of an organism.
- For example, you cannot reliably determine the height of wheat by measuring one wheat plant in a farmer’s field.
- However, if you measure the height of a number of plants and then calculate an average.
- your result is likely to be close to the average height of the entire crop.
- After measuring a sample, you can use the results of the sample to make generalisations or estimates about the number of organisms, distribution of species or measured characteristic throughout the entire habitat.
Sampling can be done in two ways
random and non-random:
Random sampling
Random sampling means selecting individuals by chance. In a random sample, each individual in the population has an equal likelihood of selection, rather like picking names out of a hat.
To decide which organisms to study, random number tables or computers can be used.
You have no involvement in deciding which organisms to investigate.
For example, to take a random sample at a grass verge you could follow these steps:
For example, to take a random sample at a grass verge you could follow these steps:
Mark out a grid on the grass using two tape measures laid at right angles.
Use random numbers to determine the x coordinate and the y coordinate on your grid.
Take a sample at each of the coordinate pairs generated.
Non-random sampling
Non-random sampling is an alternative sampling method where the sample is not chosen at random.
It can be divided into three main techniques:
Opportunistic
Stratified
Systematic
A pooter
is used to catch small insects
By sucking on a mouthpiece, insects are drawn into the holding chamber via the inlet tube.
A filter before the mouthpiece prevents them from being sucked into the mouth.
Pitfall traps
are used to catch small, crawling invertebrates such as beetles, spiders and slugs.
A hole is dug in the ground, which insects fall into.
It must be deep enough that they cannot crawl out and covered with a roof-structure propped above so that the trap does not fill with rainwater.
The traps are normally left overnight, so that nocturnal species are also sampled.
Point quadrat
this consists of a frame containing a horizontal bar.
At set intervals along the bar, long pins can be pushed through the bar to reach the ground.
Each species of plant the pin touches is recorded
Frame quadrat
this consists of a square frame divided into a grid of equal sections.
The type and number of species within each section of the quadrat is recorded (Figure 4). Further details are given below.
To collect the most valid representative sample of an area, quadrats should be used following a random sampling technique (as discussed in Topic 11.2, Types of sampling).
To study how the presence and distribution of organisms across an area of land varies, the quadrats can be placed systematically along a line or belt transect.
