4.3: Quadrates samples

Describe the use of quadrats as a technique for sampling the distribution of organisms in their habitat



• The quadrat sample that you take has to be random so there is no bias, and has to be representative (large enough) so that the estimate is as close to the true population as possible
• A grid system would be set up across the field. There would be an x and y axis, as well as numbers running across the sides of the graph
• Then random numbers would be generated for the x and y coordinate so we know where we want to place our quadrat
• Then we would count the number of whatever species we are counting.
• Your representative sample would be ideally around 10 quadrats or 10% of the whole area.
• The number of that species would be recorded into a table, then


   total of species        = number of species/m²
number of quadrats 

4.2: quadrates

recall the use of quadrats to estimate the population size of an organism in two different areas



• The sand dune ecosystem: it is made up of a number of different species of population which form the community of the ecosystem (and the habitat).
• There is a fence that splits the area in two: an ungrazed area and a grazed area (grazed by cattle and agriculture).
• quadrating: counting the size of a population.
• The quadrat is a square (0.5mx0.5m) and used to sample different areas of the land, and gain an estimate of the populations size.
• This way populations between two different areas can be compared.

4.1: Ecosystems

Understand the terms: population, community and ecosystem.




Ecosystem
An ecosystem is a community of organisms in a certain habitat

Habitat
(abiotic factors)
eg sunlight, temperature, rainfall, humidity, slope of the land, geology
note they are all non-biological

Community of organisms
made up of a population of varying species which interact with each other

Population
Number of individuals of a specific species

Species
Organisms that reproduce and make offspring

plant fertilisation - continued

in the picture below, on the very left after all the ovarys have fertilised, the stigma and the style degenerate since they are not needed any more.

after this picture, the fruit gets eaten by an animal, which excretes out the seeds with its feces, which means the seed gets the necessary nutrients to grow.

in these two pictures you see that the seeds are in the middle and the fruit outside is due to the plant sending sugars around the seeds. Note where the style and stigma have degenerated (bottom part on the red apple)

credits to savannah and harriet for the two last pictures

3.4 PLant fertlisation

• pollen grains grow all the way down the stigma, making a pollen tube
• the nucleus travels down the tube and into the ovule

A number of things will occur:
1. Ovule will fertilise that leads to formation of zygote that grows into a embrionic plant
2. Oustide of the ovule: seed coat (TESTA)
3. Formation of cotyletons (food stores for seedling)
4. Thickning of the walls of the ovary, putting things like sugar, protein that will create fruit

3.3a insect pollination & 3.3b wind pollination

• PLant sex = pollen grain (contains male nuclei) transfers from the anther of a plant to the stigma of another plant
• Insect gets attracted to a plant because of its nectar and colourful petals. Then some pollen grains get stuck on it, and as the insect goes to another plant the pollen grains transfer into that plants stigma
•There are 2 reasons why insects are attracted to plants
- Signals: SCENTS AND COLOUR PETALS
- Value: POLLEN (source of protein for insects) AND FOOD (nectaries produce fructose)



• The pollen is transfered by wind into the air from the anther to the stigma
• features of wind pollination:
- light pollen grain (wing features, which allow to move through the air efficiently)
- tall anthers so they are exposed to wind
- stigmas have large SA, and feather like surface so it can catch pollen easily
• The plant has no colours or scent to attract insects as it uses wind as its only transport for the pollen
• It would be a waste of nectar, since all the pollen is wind pollinated, so it it focuses all its energy on making pollen.

Flowers