Standard Grade Biology Revision Notes

Transcription

1 Standard Grade Biology Revision Notes The Biosphere Habitat where an animal lives Community all the plants and animals in an area Ecosystem living and non living parts (habitat + community) Population living organisms of one type Biotic factor a living factor (disease, predators) Abiotic factor a non living factor (temperature, ph) Sampling - taking a small section of the area to get an idea of as a whole. Quadrat - estimate numbers of plants. Throw randomly, take many samples (reliable), make a general rule for counting and stick to it. Tree Beating sample a tree. Do many samples, The Nitrogen Cycle The cycling of Nitrogen (needed by humans to make protein). lightening and fixing of nitrogen gas (from air) into nitrates in the soil = nitrification (nitrogen into the soil). b + f b b plant protein animal protein death and decay ammonium nitrites nitrates n n b = bacteria f = fungi n = nitrification nitrates nitrogen gas in the air (by bacteria) = dentrification (removing nitrogen from the soil).

2 Investigating Cells Animal Cells nucleus (controls cell activities); cell membrane (controls what substances can enter and leave the cell), cytoplasm ( jelly like material where chemical reactions take place). Plant Cells nucleus, cell membrane, cytoplasm, cell wall ( made of cellulose and gives cell its shape), vacuole ( contains cell sap), chloroplasts (site of photosynthesis, contains chlorophyll). nucleus (controls cell activities); cell membrane (controls what substances can enter and leave the cell), cytoplasm ( jelly like material where chemical reactions take place). Diffusion the movement of molecules from a region of high concentration a region of low concentration, until equal. Only small soluble molecules (glucose) can diffuse in and out of a cell as they have to pass through tiny pores in the cell membrane (selectively permeable). Osmosis the movement of water molecules from a region of high water concentration a region of low water concentration through a membrane and down a concentration gradient. Animal cell + water burst (no cell wall); animal cell % salt same; animal cell + strong salt / sugar shrink Plant cell + water turgid (doesn t burst); plant cell + dilute salt / sugar same; plant cell + strong salt / sugar plasmolysed Mitosis a summary The process by which the nucleus divides into two daughter nuclei, each becoming an identical copy of the mother nucleus. 1) Chromosomes appear as long strands 2) Chromosomes become shorter and thicker, made of two chromatids, joined by a centromere 3) Chromosomes line up along the equator and are attached to opposite poles by a spindle fibre. 4) Chromatids are separated as the centromere splits and they are pulled to each pole (north and south). 5) The separate chromatids are now called chromosomes and the cytoplasm starts to divide and a nuclear membrane forms around the chromosomes. 6) Two daughter cells are formed which are identical copies of the original cell.

3 Enzyme Summary Biological catalysts )made of protein) that speed up the rate of reactions. They can be breakdown (degradation) or Build up (synthesis) reactions. Substrate Enzyme End Product (what you start with) (biological catalysts) (what you end up with) Enzyme rate is affected by temperature and ph. All enzymes work best at 37 0 C. Pepsin works best at ph 2.5 and catalase works best at ph 9. Enzymes are therefore said to be specific and work best at their optimum. Enzymes work like a lock and key. The substrate is the key and the enzyme is the lock/ The enzyme remains unchanged at the end of the experiment and can be reused. Substrate Enzyme End Product Synthesis / Degradation Starch Amylase Maltose D Hydrogen Peroxide Catalase Water and oxygen D Protein Pepsin Peptides D Fat Lipase Fatty acids D Glucose 1 - phosphate Phosphorylase Starch S Living things need energy to grow, move, reproduce etc. They get this energy from Aerobic Respiration. Aerobic Respiration glucose + oxygen carbon dioxide + water + energy Metabolism the sum of all chemical processes in a living organism that keeps it alive.

4 World of Plants A Summary Plants are used for food (wheat), medicine (opium from poppies) and as raw materials (timber). The rainforest should not be destroyed as it may house new foods and new medicines. These are potential uses of plants. Germination the development of a plant embryo into a plant. It requires water(allows enzymes to digest the stored food), oxygen (for respiration) and a suitable temperature (for enzymes). Photosynthesis food production (starch) by a green plant. It needs light, carbon dioxide and chlorophyll. Enzyme controlled carbon dioxide + water + light energy sugar (stored as starch) + oxygen A seed contains 1) Seed coat protects the internal structures 2) Food store gives the young plant energy for growth 3) Embryo plant grows into the plant Pollination the transfer of pollen grains from the anther to a stigma. It can be selfpollination or cross-pollination. Cross-pollination can be done via the wind or an insect (e.g. bee). Insect Pollination Flowers - responsible for the reproduction of the plant (ovules are female gametes and pollen are male gametes). 1) Petal bright in colour to attract insects 2) Stamen male part, contains pollen. Divides into the anther (splits to release pollen) and the filament. 3) Ovary female part, contains ovules 4) Nectary makes sugary nectar that insects eat 5) Sepal protects the unopened flower. 6) Stigma pollen grains attach here, it is sugary and sticky. Once a pollen grain has landed on a stigma, it responds to sugar on the stigma and uses it as energy to produce a pollen tube, which grows down the stigma. The nucleus of the pollen grain travels down to reach the ovule where the male and female gametes fuse forming a zygote (fertilisation). Wind Pollination The flowers are small and do not have bright colours or a nectary (they do not need to attract insects). The anther is attached loosely and hangs out of the flower (allows them to be shaken). The pollen grains are light and smooth and a large quantity is produced (allows them to be carried by the air and there is a smaller chance of the pollen reaching the stigma). The stigmas are feathery and hang outside of the flower (in a good position and a larger surface area for trapping pollen). Seed formation from the ovule

5 Fruit Formation from the ovary wall (soft and fleshy) Seed Dispersal wind (light); animal internal (bright coloured and juicy); animal external (hooked); self- explosive (bursts open). Asexual Reproduction Also called Vegetative Propagation. New plants are formed from a single parent plant (no sex cells or fertilisation). The offspring are genetically identical to the parent. Runner a new plant develops at the end of a stem called a runner (spider plant) Tuber use of old tuber to provide energy for the growth of a new plant and other tubers (potato). Advantages young plant has its own food store; young plant produced in a suitable environment; no pollination. Disadvantages competition with parent plant; inherited all characteristics from parent so if a disease kills the parent death. Artificial Propagation An artificial way to reproduce a plant asexually. Cuttings small section of the plant allowed to grow roots and then into a new plant. Grafting joining two cut surface of plants (usually to get a combination of good characteristics). Clone an identical copy. Transport Systems All living plants need water and sugar to stay alive. Phloem sugar transport in all directions. The tissue is alive. Xylem the transport of water (and minerals) upwards only. Xylem is dead. Xylem contains lignin, which is responsible for providing support. Plant Structure 1) waxy cuticle waterproof to stop water evaporating 2) upper epidermis top layer, allows light through. 3) palisade mesophyll photosynthesis (contains chloroplasts) 4) leaf vein xylem and phloem 5) spongy mesophyll - photosynthesis (contains chloroplasts) 6) air spaces between spongy mesophyll and allows gas exchange 7) stomata pores to allow entry and exit of gases and water loss (most on lower surface) 8) guard cells change shape to control entry and exit of gases, (close in dark or when loosing too much water). Testing a leaf for Starch 1) boil leaf in water (bursts cell membranes) 2) place leaf in alcohol ( dissolves chlorophyll, removing the green colour) 3) Put leaf in warm water (softens it) 4) Test with iodine solution (blue black colour = starch).

6 Limiting Factors a factor that holds up the process of photosynthesis because it is in short supply ( light intensity, carbon dioxide concentration, temperature).