Biology - IGCSE : MRS GREN, Animal and Plant cell, Photosynthesis, Respiration, DNA, Variation, Graphs, The Five Kingdoms

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MRS GREN (H)

Movement - the ability to change position

Respiration - releasing energy from glucose

Sensitivity - the ability to detect and respond to a stimula

Growth - the ability for cells to divide

Reproduction - the ability to create offspring

Excretion - getting rid of metabolic waste (eg. urea, CO2)

Nutrition - the need of metabolic substrates

Homeostatis / Control - controlling your internal environment (eg. keeping yourself at 37°C)

PLANT & ANIMAL CELLS

Cell wall - made of cellulose. Gives the cell its shape and support.

Cell membrane - controls what enters and leaves the cell. Like a sac, contains all the cells contents.

Chloroplasts - organelles that contain chlorophyll, which is needed for photosynthesis. Absorbs light and makes glucose. Gives green pigment.

Nucleus - controls the cell functions. Carries DNA of the cell.

Vacuole - sac that contains cell sap. 98% water. Store for waste, amino acids and sugars.

Cytoplasm - fluid that fills the cell, called protoplasm. 80% water and colourless.

PHOTOSYNTHESIS - How do plants live?

- The process of using light energy to make glucose sugar.

- Chloroplasts contain chlorophyll

- Chlorophyll's job is to absorb light energy

- Chloroplasts then store a lot of the produced glucose by turning it into starch.

Carbon Dioxide + Water -> Oxygen + Glucose

Plants need minerals to survive and grow. Poor plant growth is usually because there is a deficiency in one or more minerals.

Plants need nitrate to build proteins and help the growth. Leaves turn yellow when it lacks nitrate.

Plants need magnesium for photosynthesis. Leaves turn yellow. Chlorophyll molecules contain magnesium ions. Magnesium absorbs light.

Amino acids are building blocks for protein. Amino acids contain nitrate.

LEAF STRUCTURE

Stomata lets in CO2

Stomata lets out O2

Respiration

To breathe in....

- Diaphragm contracts and flattens

- Lungs are pulled downwards

- Volume of lungs increased

- The pressure of the air inside is lower than the external air pressure

- To balance the air pressure, air rushes in from the outside, and the lungs inflate.

NB. The opposite events occur when you breathe out.

trachea

left lung

diaphragm

Inhaled

4/5 nitrogen

1/5 oxygen

trace of CO2

Exhaled

4/5 nitrogen

3/20 oxygen

1/25 CO2

DNA

Almost every cell of every organism can only survive if it aerobically respires ie. releasing energy from glucose. Aerobic respiration requires oxygen

Glucose + Oxygen -> Carbon Dioxide + Water

C6 H12 O6 + 6CO2 -> 6CO2 + 6H2O

Nuclei of most human cells contain 46 chromosomes.

Each chromosome is made of two very long chains of DNA wrapped together. So chromosomes contain DNA not the other way round. DNA stands for Deoxyribo Nucleic Acid.

A DNA strand consists of three components that repeat over and over again:

Sugar

Phosphate

Base

There are four different bases :

Guanine

Cytosine

Adenine

Thymine

G only bonds with C

A only bonds with T

A gene is a small stretch of DNA. All a gene does is code for a characteristic. The order of the bases in the gene is specific to what characteristic the gene codes for.

DNA is organisms can just randomly mutate. This mutated DNA will give the organism a new feature. The organism is now varied from the others of the same species. If this feature is beneficial it is called an adaption.

VARIATION

There are two causes of variation:

The environment

- language spoken

- hair length

- religion

2. Your DNA

- natural hair colour

- gender

- tongue rolling

Many characteristics can be affected by both :

- freckles

- weight

- skin colour

Variation can also be classified into two types:

Continuous

- the feature can take any value between the maximum an the minimum

- hair length

height

2. Discontinuous

- the feature can take one of a few set types

- eye colour

- gender

- blood type

Most of the time, if a variation is continuous, it's environmental.

Variation in humans:

- hair colour

- eye colour

- gender

- height

- weight

- tongue rolling

- freckles

- dimples

- skin colour

GRAPHS

Bar charts

- gaps needed

- discontinuous

Histograms

- touch

- continuous

- small number of categories

- 4 or 5 group ideal

Scatter Graphs

- two sets of continuous

- height and weight

- no line

Line graphs

- independent + dependent variable

- how it is affected by the first variable

- independent goes on the horizontal axis

- line joined point to point

THE SIX KINGDOMS

Kingdom KING

Phylum PLAYS

Class CHESS

Order ON

Family FRIDAYS

Genus (with) GREEN

Species PIECES

Animals

- multicellular

- cannot photosynthesise

- no cell walls

- can move from place to place

- store sugars as glycogen

human

chimpanzee

Plants

- multicellular

- can do photosynthesis because they contain chloroplasts

- have cell walls made of cellulose

- store sugars as starch

pine tree

rose

Fungi

- can be single celled (yeast) or multicellular (mucor mould)

- cannot photosynthesis

- body is made of threads called hyphae arranged into a mycelium

- have cell walls made of chitin

- feed by saprotrophism

- digest food outside their body then absorb it

- can store sugars as glycogen

Bacteria or monera

- single celled

- have cell wall but no nucleus

- some can photosynthesise

salmonella

pneumococcus (causes pneumonia)

lactobacillus

streptococcus

lact. & stre. are used to make yogurt

Protista or protoctista

- single celled

- some are animal like (amoeba)

- some are plant like (chlorella)

- some cause disease (plasmodium cause malaria)

Virus

- much smaller than bacteria

- can infect any other organism

- doesn't have a cellular structure

influenza

ebola

HIV (causes AID's)

TMV (Tobacco Mosaic Virus)

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