Igcse Bio Notes

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IGCSE Biology Notes

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Unit 1 : Characteristics of living things

Biology is the study of living organisms. For something to be alive it needs to perform all seven functions of living things.MRS GREN Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition. 1. Movement Most organisms are able to move their whole body even plants can shift their stem towards the sunlight and their roots move towards healthy soil. 2. Respiration IT is the breakdown of food inside a living organism IT IS VITAL for survival. 2 types Aerobic Respiration which involves O2 & glucose breaking down to form CO2 water & ENERGY. Anaerobic Respiration which is the incomplete breakdown of food. Happens when there is not enough oxygen. Equation, Glucose & O2 (not enough) to form CO2 Lactic Acid or Alcohol (depending on the organism) & a little ENERGY. 3. Sensitivity It is the ability to detect and respond to a stimulus. 4. Growth It is the permanent increase in size and quantity of cells using materials absorbed from the environment. 5. Reproduction It is forming new individuals of the same species either sexual (2 parents) or asexual (1 parent) \ 6. Excretion It is removal of harmful products of metabolism. Egestion is the removal of undigested products which haven’t entered the cell. 7. Nutrition It is the intake of food material from the environment. Autotrophic nutrition: Organisms that make their own food such as plants. Heterotrophic nutrition: Organisms that need readymade food including herbivores, carnivores & omnivores.

Unit 2 : Classification
Classification is sorting organisms into smaller groups based on their similarities which then allows us to make comparison between them. Organisms are split into the following:

• • • • • • •

Kingdom Phylum Class Order Families Genus Species

Many Organisms

Few features in common

Individual Organism

Many features in common

A specie is a group of organisms that share the many similar appearances and can bread with each other. Species are scientifically named by two names in Latin to avoid differences in languages. The first name is the name of the genus while the second name is the species name e.g. WOLF (Cannis Lupus) (must be italic and underlined) The main groups of living are the 5 kingdoms. They don’t include virus since it doesn’t obey some characteristics of life. The five kingdoms are: Bacteria, Protoctista, Fungi, Plants, and Animals.

Virus
The size of a virus about 30-300 nm and its only visible with an electron microscope. IT has a protein coat around the DNA or RNA sometimes has spikes. It has no cell structures. How a virus multiplies 1. Virus ejects its DNA or RNA into the cell 2. The genetic material multiplies 3. Mew viruses are formed inside the cell and then burst out of the cell.

Bactria
The size of bacteria is about 0.2 to 10 um. It is only seen under high powered microscopes. Structure: No Nucleus • No mightocondria

• • •

No chloroplast in most of them They are either saprophytes or cell wall (not made of cellulose)

parasites

Bacteria reproduce asexually by binary fission every 20 min’s (if conditions are suitable) IF conditions are not well some species can for spores for survival.

Fungi
• • • Mostly multicellular (many cells) (yeast is an exception) Cell wall made of chitin IT has cytoplasm & it may be a saprophyte or a parasite



It reproduces asexually by spore formation or by budding (in yeast) but in bad conditions it reproduces sexually for survival

Yeast budding

Single fungi cell Structure of a mould fungus

Budding is when a yeast cell splits into two cells and it keeps happening over and over again numbers can get up to millions in just a day. A mushroom is an example of a parasitic fungus.

Plants

Plants produce seeds from inside the flower. The plant kingdom is divided into algae, ferns, mosses, and seed plants. Seed plants are divided into conifers and...
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