Revision for Additional Biology

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Plant Cells

Plant Cells:

Cell wall - made of cellulose which supports cell

Vacuole - cell sap

Chloroplast - Photosythesis occurs, contains chlorophyll

Nucleus - contains genetic info which control activities of cell

Cytoplasm - chemical reactions happen, contains enzymes.

Mitochondria - Respiration takes place here

Ribosomes- proteins are made. 

In a leaf:

the waxy layer- stops water escaping

upper epidermis- transparent layer to let light through

palisade mesophyll- cells contain chloroplast trap light.

spongy mesophyll- has air spaces to allow gases in and out

xylem and phloem- tubes bring water and take away glucose

lower epidermis- layer with stomata (allow gases to diffuse in and out of leaf)

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Animal, Yeast and Bacteria Cells


Nucleus- contains genetic material, controls activities of cell

Cytoplasm- chemical reactions happen, contains enzymes

Mitochondria- Respiration

Ribosomes- proteins are made


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Types of Fossils and Extinction

Gradual Replacement - By Minerals replacing bones ect. Form rock like substance.

Casts and Impressions - In places like clay and mud.

Preservation - In environments where no decay can happen.

Causes for Extinction: 

The Environment Changes too quickly.

New predator

New disease

Cannot compete

Speciation (new species develops)

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