Year 10 0610 Biology Revision Notes:

Life processes - Name and explain each of the 7 processes common to all living things using the mnemonic Mrs Gren

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Understand that in some organisms these processes are not obvious.

e.g. the dormant stage of plant seeds, corals and sponges, lichen etc.

Classification: Understand how all living things can be classified according to similarities.

Read this general article from the BBC:

BBC How did life begin?

CIE, only 5 Kingdoms:

- Prokaryotes: (Bacteria and Archaea)

and Eukaryotes:

- Animalia (Vertebrates and Invertebrates)

- Plantae

- Fungi

- Protokcista (Protists, protozoa etc.) A group of unrelated organisms which do not belong in the other 4 Kingdoms.

Using Keys:

Identify organisms using a key. Carefully follow instructions to identify unknown organisms, of different species or of closely related organisms.

Animals:

Invertebrates; The largest group of Animalia.

Divided into several Phyla (Phylum) according to their structure.

Arthropods - Jointed legs, hard external skeleton

e.g. Crustacea (Crabs, lobsters)

       Arachnida (Spiders, scorpions  8 legs)

       Insecta (Beetles, flies, wasps - 3 body parts, 6 legs, 2 pairs of wings)

       Myriapoda (Many legs - centipedes, millipedes, segmented body)

Molluscs - soft body, muscular foot, shell sometimes present

e.g. Cephalapods - octopus, squid

       Gastropods - slugs, snails, nudibrancha, clams

Echinoderms - spiny skin - Starfish, sea urchins

Porifera - Sponges

Cnidaria - Jellyfish and corals

 Annelida - Segmented worms - earthworm

 Flat worms - Flukes and tapeworms - parasites

 Nematodes - Roundworms, or unsegmented worms - most are parasites.

Vertebrates:

Fish, adapted to life in water, scales on their skin, breathe with gills. Ectothermic - 'cold blooded'

Amphibeans (2 stage life-cycle) moist skin, lay eggs in water, first stage have gills. Ectothermic.

e.g. frogs, toads, salamanders

Reptiles - evolved thicker skin, eggs with shells to move away from water. Ectothermic.

e.g. Lizards, snakes, crocodiles, turtles.

Birds - Some reptiles evolved into Birds, hard shelled eggs, feathers, endothermic -'warm blooded'

Mammals - Some reptiles evolved into mammals - produce milk, live young (apart from Monotremes), fur, endothermic. Some mammals returned to water, whales and dolphins.

Plants - evolved from plant-like protists. Green algae (seaweed)

Plants possess chloroplasts for photosynthesis.

Moved on to land as Mosses 400 mya (no roots, small leaves, reproduce using spores, live in wet places.)

Ferns evolved vascular tissues (wood) for support. Better adapted to land, Reproduce by spores (male and female gametes (sex cells) that swim in water.

300 mya Conifers appeared - suited to colder, drier climate. First seeds, produced in cones. Gymnosperms - naked seed.

165 mya first flowering plants appeared - Angiosperms (covered seeds) Seeds protected in an ovary which forms a fruit.  Today 80% of all plants are flowering plants.

2 main groups: 

Monocotyledon (seed has 1 cotyledon as food store) parallel veins in leaves, long thin leaf. e.g. rice, grasses, orchids

Dicotyledon - (seed has 2 cotyledons) branched veins in leaves e.g. most flowering trees, bean plants.

Cells

All cells have:  a cell membrane, nuclear material, cytoplasm. (apart from mammalian blood cells which have lost the nucleus.

Understand all cells are fundamentally similar apart from:

Prokaryotes have no nucleus

Fungi have cell walls made of chitin.

Plants have a visible vacuole, a cellulose cell wall and may contain chloroplasts.

Most cells are HETEROTROPHIC (feed on organic molecules)

Plants cells are AUTOTROPHIC (can make their own food by photosynthesis)

You need to know the functions of the different parts of the cell.

Magnification:

Cells are small and only visible under a microscope. 

Magnification = Apparent size/Real size.

At 400x magnification, if a drawing of a cell is 10mm, the real size must 1/400th the size.

10mm divided by 400 = 0.025mm   1000 micrometres = 1mm.

0.025mm = 25 micrometres.

Blood cells are even smaller, 15 micrometres - can squeeze through narrow capillaries, no nucleus to save space.

Bacteria - about 2 micrometres

Virus - 0.1 micrometre

Plant Cells

Cellulose cell wall, large vacuole filled with cell sap (aqueous solution), nucleus, maybe chloroplasts.

Root hair cells - adapted to take in water and minerals from soil.

Xylem - long thin tubes that carry water from roots to leaves.

Guard cells - pair of cells in a stoma (stomata) holes in leaves allowing gas to enter and leave.

Organisation of cells:

Organelle (inside cell) ------Cell-----Tissue--------Organ---------Organ system---------Organism

Movement In and Out of Cells

Diffusion -

no energy needed- random movement of particles in a liquid or gas (kinetic energy, collisions) until particles evenly distributed EQUILIBRIUM

Osmosis

- diffusion of water across a semi or partially permeable membrane (cell membrane) from a high water potential to low water potential or dilute solution to a more concentrated solution. No energy needed.

Solution: Solute (solid) dissolved in Solvent (e.g. water - aqueous solution)

Active Transport - 

allows movement of particles against a concentration gradient e.g. mineral ions into root hair cells.  - Needs ENERGY. Uses carrier proteins.

Phagocytosis

-Some cells engulf molecules by flowing around them e.g. white blood cells, amoeba.

Organic molecules

Found in all living things.

Organic molecules contain chains, branches and rings of carbon atoms.

They also contain hydrogen, and usually contain oxygen.

4 main groups:

Carbohydrates - sugars and starches

Proteins

Lipids - fats and oils

Nucleic acids - found in genetic material

Carbohydrates

monosaccharides - single or simple sugars, soluble in water, e.g. glucose and fructose

disaccharides - double sugars e.g. sucrose, maltose, lactose

polysaccharides - long chains and branches of monosaccharides e.g. starch, glycogen, cellulose

Proteins

Long chains or branches of amino acid sub-units (20 different amino acids) can make almost limitless different proteins. The order of amino acids is controlled by GENES in the nucleus.

Lipids

3 chains of FATTY ACIDS joined together by a molecule of GLYCEROL

Found in plants and animal cells.

Food Tests

You must learn the 4 main tests for the different groups, the names of the reagents and the colours for positive and negative tests.

                           

Enzymes

Enzymes are special proteins that control all biochemical reactions in METABOLISM.

They are Biological Catalysts, which mean they speed up reactions but themselves remain unchanged.

Without enzymes, biochemical reactions would be too slow.

Lock and Key mechanism - enzymes are SPECIFIC, they only work in a single reaction.

The enzyme shape controls the reaction.

SUBSTRATE molecules (small molecules) are built into large ones, PRODUCTS.

Large molecules can be broken down again into small ones.

Enzymes are affected by:

Temperature - too cold, not enough energy, too hot, enzyme is killed, DENATURED.

Best temperature is OPTIMUM TEMPERATURE.  Animals 37 degrees C. Plants 25 degrees C.

pH - acid or alkaline. Varies according to where the enzyme acts. pH 6 in mouth, pH 2 in stomach etc.

Catalase - breaks down hydrogen peroxide

Lipase - breaks down lipids

Amylase - breaks down starch

Protease - breaks down protein

Lactase - breaks down lactose in milk

Enzymes in the mouth - salivary glands - amylase

Stomach - produces lipase and protease

Pancreas - produces many enzymes including amylase and lipase

Small intestine - more enzymes such as lactase, sucrase etc.