A gradual change in the distribution of species across a habitat
Define a Community
All the organisms living in a particular area
How can the distribution of organisms be shown?
It can be mapped using a transect line and displayed using a kite diagram
What did Van Helmont say about photosynthesis?
He concluded that from his experiment that the growth of plants couldn't be purely down to the uptake of soil minerals, it had to be something else. He found this when he experimented by growing a willow tree.
What did Priestly's experiment show?
That plants produced oxygen
How can the rate of photosynthesis be increased?
More carbon dioxide, More light, a higher temperature which increases the enzyme action
What are the two stages of photosynthesis?
1. Water is split up by light energy releasing oxygen gas and hydrogen ions. 2. Carbon dioxide gas combines with the hydrogen ions producing glucose and water.
What did Greek Scientists believe about photosynthesis?
That plants took minerals out of the soil to grow and gain mass
How is the outer epidermis in a leaf adapted for photosynthesis?
It lacks chloroplasts so it is transparent which means there are no barriers to the entry of light.
How is the upper palisade layer of a leaf adapted for photosynthesis?
It contains most of the leaf's chloroplasts as it will receive most of the light.
How are the spongy mesophyll cells adapted for photosynthesis?
They are loosely spaced so that diffusion of gases between the cells and the outside atmosphere can take place.
Why is the arrangement of the mesophyll cells in a leaf important for photosynthesis?
The arrangement of these cells create a large surface area to volume ratio so that large amounts of the gases can enter and exit the cells.
What pigments does a leaf have in it?
chlorophyll a and b, carotene and xanthophylls
Why do plants have three pigments in their leaves?
To maximise the use of the Sun's energy as each pigment absorbs light of different wavelengths.
Why do leaves have vascular bundles?
For support and the transport of chemicals such as water and glucose.
How can population size be estimated?
It can be estimated by obtaining data from a small sample and scaling up. You could use the capture - recapture method.
What is the equation for the capture - recapture method?
Population size = number in 1st sample x number in the 2nd sample / number in 2nd sample previous marked
What does the capture - recapture method assume?
1. There are no deaths, births or movement of the organisms.
2. Identical sampling methods for both samples
3. The markings do not affect the survival of the organisms
What is Osmosis?
A type of diffusion that depends on the presence of a partially- permeable membrane that allows small molecules like water to pass but not bigger ones like glucose.
What is diffusion?
The net movement of particles in a gas or liquid from an area of high concentration to a low concentration due to the random movement of the particles
What are dicotyledonous plants
What are Phloem cells?
Living cells that are arranged in columns
What do the Xylem and phloem cells form?
Vascular Bundles in dicotyledonous plants (broad leaved)
What do phloem carry?
What do xylem carry?
What is the turgor pressure?
The pressure exerted in the cell membrane by the cell wall when the cell is fully inflated
What does 'turgid' mean?
When plant cells are full of water with their walls bowed out and pushing against neighboring cells.
What is lysis?
When too much water enters the cell and the cell swells up and bursts
What is crenation?
When too much water leaves an animal cell it shows crenation by shrinking into a scalloped shape
What does organic farming not use?
Artificial fertilisers or pesticides
What does 'Biological Control' do?
It uses living organisms to control pests
What type of digestion does Saprophytic fungi use?
Why are earthworms, maggots and woodlice called detritivores?
Because they feed on dead and decaying material. (detritus)