Biology Unit 2

Animal and Plant Cells

The different parts of the cells are called organelles.


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Microbial Cells

Yeast is a single celled fungus. Its cells have cell wallls but they are not made of cellulose like plant cell walls.

Algae are simple, plant like organisms.

Bacteria do not hace a nucleus. Their genes are in the cytoplasm.


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Diffusion is the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region with a higher concentration to a region with a lower concentration.

Most cells need oxygen to respire.

Oxygen diffuses into the cells.

The concentratino of oxygen is kept low inside the cell as the cell keeps on using it up.

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Speicalised Cells

The human body contains hundreds of different kinds of specialised cells.

A specialised cell is designed to perform a single task.


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The cells that make up tissues are adapted for particular roles.

Muscular tissues are specialised to produce movement.


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Animals Tissues and Organs

A system is a group of organs that performs a particular function.

The function of the digestive syetem is to break down the food you eat so the molecules can enter the blood.


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Plant Tissues and Organs

The organs in a plat are made up of tissues.

The whole plat is covered in a layer of epidermis, this helps to protect the underlying cells, stops the leaves losing too much water.

Most of the cells in a leaf are mesophyll cells, this is where photosynthesis takes place.

Xylem and phloem tubes run through the entire plant. Xylem carries water from roots to leaves, phloem transports sugar.


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The word equation for photosynthesis is:

Carbon Dioxide + Water -----> Glucose + Oxygen

In photosynthesis, light energy is stored in glucose molecules.

The energy is transferred to animals when they eat the plants.

Glucose can be converted into starch and stored for later use.

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Limiting Factors

Light is a limiting factor for photosynthesis.

There comes a point when the rate of photosynthesis does not increase any more, no matter how much more light it is given.


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The Products of Photosynthesis

Glucose is made from carbon, hydrogen and oxygen atoms. Plants make other substances from glucose.

To convert glucose into proteins, plants need nitrogen which they get in the form of mineral ions. They  normally use nitrate ions and absorb them from the soil through roots.

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Distribution of Organisms

Temratue affects the distribution of organisms as many species can only live in a specific tempratue range.

Another would be availability of nutrients as very wet soils are usually low on nitrate ions, so only certain plants can live there. Animals can only live where food is.

The amount of light is also a factor as plants and algaes need light for photosynthesis.

Another is availability of water as all organisms need water to survive, species that live in deserts have sepcial adaptations to help them obtain and store water.

The amount of oxygen is also a factor alond with carbon dioxide and most organisms need oxgyen to survive, and plants need carbon dioxide for photosynthesis.

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Using Quadrats to Sample Organisms

Quadrats can be used to measure the distribution of organisms in a habitat. It is best to place the quadrats randomly.

You can either count the number of each species of estimate the percentage of the area that each species takes up.

This process should be repeated multiple times.

A transect is used to find out is the distribution of organisms changes as you move from one habitiat to another.

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