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Bio Revision Year 11 Definition • Asexual reproduction is the process resulting in the production of genetically identical offspring from one parent. Advantages of Asexual Reproduction • • • • • Only one parent is needed. It takes a very short period of time No Fertilization Identical characteristics to parents Asexual reproduction is more reliable because there are less steps to follow so less can go wrong. Disadvantages of Asexual Reproduction • Almost no chance of an evolution taking place. • Identical to the parents, so diseases and bad qualities are also passed down • Struggle for light, space, nutrients and soil so most plants will remain less healthy. • Some plants produce side branches with plantlets on them. • The spider plant, Chlorophytum, does this. • Other plants, such as strawberries, produce runners with plantlets on them. Mitosis This is the type of cell division that happens in normal body cells. It results in a cell splitting into two identical cells. (daughter cells) In some parts of a plant or animal it happens rapidly all of the time – skin. Chromosomes line up ready for division. Chromosomes in nucleus are copied. There are the same amount of Chromosomes here as there are here 2 identical diploid daughter cells produced. Cell division starts and chromosomes start to separate. Summary... Sexual reproduction • Process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring. Meiosis This occurs in the sexual organs (testes and ovaries) to produce gametes. The chromosome number is reduced by half. Each of the 4 gametes produced are slightly different from each other. Chromosomes are copied by a cell in the reproductive organs. The cell divides into two new cells 4 gametes are genetically different. There is variation. The cells divide to produce 4 haploid daughter cells (gametes) Getting them to meet! Plant Parts • • • • • Sepals – Protect the petals Petals – Attract insects Anthers – the male part of the plant Stigmas - the female part of the plant Ovaries – where the egg develops Flowers • • • • • sepals, petals, anthers, stigmas ovaries Figs. 30.7 & 38.2 Pollination • the transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma) Insect-pollinated flowers are adapted to attract insects to them to enable transfer of pollen Pollen has barbs for hooking onto insect fur nectar and a scent present Anthers positioned to rub pollen onto insects Sticky stigma to collect pollen Flower Structure Pollination Brightly coloured petals Fertilisation Seed Dispersal Germination Test Pollen can be carried between flowers by insects or by wind Flower Structure Pollination Fertilisation Seed Dispersal Germination Test Wind-pollinated flowers are different in structure because they do not have to attract insects to them but do need to be exposed to the wind. Pollen grains are very small and light. They occur in very large numbers Anthers are exposed to the wind so that pollen can easily be blown away Stigma are feathery to catch pollen carried on wind Petals are small and green as there is no need to attract insects Flower Structure No scent or nectary Pollination Fertilisation Seed Dispersal Germination Test Seed Dispersal Why? • Moving away so won’t compete for • Light • Space • Water – Limiting factors! Seed parts • • • • Micropyle - where the pollen tube enters/d Radicle – First roots (and first overall part) Plumule – first shoot Cotyledon – first leaves Sexual Reproduction • 2 Parents! Male Parts • Sperm from the Testes travel through the sperm duct to leave through the penis Female parts • Eggs are released from the ovary and travel down the oviduct. • Here they meet sperm coming in from the vagina and the fertilized egg implants in the uterus • The ½ DNA egg is fertilised by the ½ DNA sperm to make a whole cell • This embyro gestated and grows into the new creature Hormones cause periods So... • FSH, Oestrogen, LH – again • FSH, Oestrogen, LH – again • FSH, Oestrogen, LH – again • FSH, Oestrogen, LH FSH • Makes an egg mature in ovaries • And causes what to be released? Oestrogen • Develops Lining of Uterus • Blocks FSH and causes what to be released? LH • Blocks Releases Egg –(because the linings there now) • TA DA And in pictures ... Artificial Control of Fertility •So ... We want no baby – therefore no egg •So, no FSH –So give Oestrogen Chemical methods • Gives the body extra Oestrogen Artificial Control of Fertility •Want Baby –We need Egg •So lots of FSH Other methods of stopping fertilization • Barriers • Stop the sperm reaching the egg The Placenta Provides nutrients to and removes waste from the foetus Blood NEVER mixes Baby growth Amniotic fluid • A water filled crash helmet! After Birth: Feeding • Bottle milk is good … • But breast milk is more – Natural – Cheaper – Contains antibodies Sexually Transmitted Disease - STD • Gonorrhoea – It burns when you pee – Yellow puss comes out of your genitals HIV/AIDS • Attacks the body’s defense cells • It is spread through – Sexual contact – Non sterile needles Growth vs Development • Growth Development Seeds do the same • But they need the right – Temperature – Amount of water We grown and develop because of our GENES Going in • Starting in a nucleus we can find a chromosome • We have 23 pairs Genes • Genes make up a bit of the Chromosome Alleles are different versions of the same gene DNA • The Actual Double helix which makes up the Genes Sex Chromosomes • The Y (Male) chromosome is missing bits) Key Terms • genotype as genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG) • phenotype as the physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed) • dominant as an allele that is expressed if it is present (e.g. T or G) • recessive as an allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g) • homozygous as having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding ( HOMO = THE SAME) • heterozygous as having two different alleles of a particular gene (e.g. Tt or Gg), not purebreeding (HETERO = DIFFERENT) Eye • All the possible combinations Eye Colour Example • Blue Eyes or Brown Eyes • You can have homozygous (the same) alleles • Or Heterozygous (different) alleles So what children would they get? • Brown Eyed Dad • Blue Eyed Mum • All babies have one of each • But as Brown is dominant it will be the eye colour Two brown eyed people making blue eyed babies? • Brown eyed mum (hetero) • Brown eyed dad (hetero) • There is a chance that the two recessive genes may meet and make a blue eyed baby So we are all different Some difference are clear cut • Being Male or Female? • This is discontinuous variation But height there is an obvious link • This is continuous Mutation • Makes us different • Some can be disadvantageous Others could be good Downs Syndrome • An extra chromosome causes downs syndrome Mutations cause changes and the best changes win and are passed on It could happen… • Naturally – Natural selection – The best wins • Artificially – Artificial selection – We pick the one to win Genetic Engineering • More direct – We take the genes that we want and put them into the animal we want So plants make food (photosynthesis) • And these are eaten by herbivores • And these are eaten by carnivores • Or omnivores (they eat everything) It starts with the sun But lots gets reflected And some is used up moving etc • Lost as: – Waste – Growth – Movement – Heat … etc How can we get better returns? • Plants – Improve growth rate – Increase size – Make resistant to pests/competition – Standardising size – Use fertiliser and improve their uptake How Wheat has changed • So this bit of Gladiator was wrong! Energy goes in cycles Water Cycle And when you have what you want The numbers gr ow 1. Grow slowly at the start (Lag Phase) – There’s not many of them! 2. But then they get lots (Log Phase) – Because they have what they need 3. And then it starts (Stationary Phase) – But then there isn’t enough for any more 4. Then they die (Death Phase) – If they make something that kills them • This doesn’t always happen Our population increase is causing problems More people means more food Fertilizers to add minerals Or even pesticides • To kill bugs Food residues • These can also be eaten in food. But fertilizers can cause problems • EUTROPHICATION • • • too much plant growth Plants die rot and decay decay uses up oxygen Also pollution Sulphur dioxide • Causes acid rain Carbon dioxide (and other greenhouse gases) • Global Warming – Melted ice caps – Rising seas So we should conserve our planet • We may need it • This tree makes a drug used to fight cancer • Wild wheat has been cross bread to help when our wheat gets attacked by bugs And that's it Good Luck!