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Biology 1 Edexcel Science Overview Revision Notes.

Extracts from this document...

Introduction

´╗┐Grouping living things: We can group living organisms based on external characteristics (phenotype). Some characteristics are unique to a group (such as feathers) and some are common to several (backbone). Five vertebrae groups are: 1. Fish 2. Amphibians 3. Reptiles 4. Birds 5. Mammals Vertebrates are either cold-blooded (poikilothermic) or warm blooded (homeotherm). Fish, amphibians and reptiles are piokliotherms. Birds and mammals are homeotherms. All living things are grouped into one of five kingdoms 1. Animalia ? multicellular; cells do not have chlorophyll or a cell wall; they feed hetrotrophycally (find food from their environment) 2. Plantae ? Multicellular; cells have chlorophyll and a cellulose cell wall; they obtain food autotrophycally (make food by photosynthesis) 3. Fungi ? Multicellular; cells do not have chlorophyll and are surrounded by a cell wall NOT made out of cellulose. They feed Saprophytically (on dead organic matter) 4. Protocista are unicellular but with a nucleus 5. Prokaryote ? Unicellular without a distinct nucleus ________________ CLASS;ORDER;FAMILY;GENUS;SPECIES A species is a pair of two species that are able to breed together to produce fertile offspring. However, this is not always the case. Plants often produce fertile offspring and not all organisms reproduce sexually (some a-sexually) Identification, variation and adaptation There is continuous and discontinuous variation. Discontinuous includes eye colour and hair colour (limited options) whereas continuous includes height (constantly changing and has many different options) Tongue rolling is discontinuous variation as people can either roll their tongue or not roll their tongue. 1. Variations such as those seen in hybrid ducks, which have characteristics of both parent species, can make classification complicated. 2. Ring species refers to chain of species that are closely geographically connected. Species within the chain show variation, they can still interbreed and produce hybrid offspring. However, the variations between the species at each end of the chain are so great that they cannot interbreed. They are distinct species. ...read more.

Middle

Plant hormones in food production Copies of plants can be made by taking cuttings and dipping the end in rooting powder. This contains plant hormones that encourages cut stems to develop roots. Fruit that can be picked unripe are subjected to ?ethane? gas to ripen them. Because some herbicides contain plant hormones that stimulate the growth of plant stems, the rate of root growth does not keep pace with stem, the roots are not able to absorb enough water to support the growing plant and it dies. Herbicides only affect the weeds because they are broad-leaved and absorb more herbicides than narrow-leaved crop plants. Growers can produce seedless fruits by smearing the plants? female sex organs with auxin paste, to stimulate the development of the fruit. However, the egg cells within the female sex organs have not been fertilized so seeds are not produced. (Fertilisers can be given to not produce seeded fruit.) Drugs Smoking and alcohol abuse Types of drugs: 1. Painkillers 1. Morphine which will deaden pain or affect the way we think about it. Pain is very psychological 1. Hallucinogens 1. Cannabis, LSD, Solvents ? produce sensations of false reality 1. Stimulants 1. Caffeine which increases the speed of our reaction time 1. Depressants 1. Alcohol, slows the activity of the brain and reaction time A person can be addicted to a drug because it gives a false sense of well-being which the person craves when it goes away. Or The body gets used to a change taking place within its tissues and craves this change more. Painkillers Block the release of neurotransmitters into the synapses, which separate the neurons Stimulants enhance the release of neurotransmitters Reaction time ? How long it takes for a person to respond to a stimulus. This depends on how quickly and how much neurotransmitter is released. Legal drugs Cigarette smoke contains many chemicals such as carbon monoxide (which reduces the amount of oxygen that red blood cells can carry), Nicotine which is an addictive stimulant that raises blood pressure and risk of heart disease and Tar which contains substances that can cause cancer and emphysema. ...read more.

Conclusion

Plants absorb CO2 from the environment, photosynthesis enables sugar production. The sugars can be used to form other parts of the plants body such as proteins 2. Plants eat animals, which take in the carbon. The transfer continues as each animal eats another, usually in increasing quantities. 3. During respiration, organisms release carbon dioxide into the atmosphere (and it is released by fossil fuel burning) Chalk is formed from fossilized remains of sea creatures. Explosed to rain the chalk dissolves and more CO2 is released. Nitrogen Cycle We can not access the nitrogen in the air. Nitrogen fixing bacteria in the root nodules of leguminous plants or in the soil can use this gaseous nitrogen to ?fix? nitrogen gas ammonia. Plants absorb the compounds in solution from soil and animals obtain it from eating the plants. Proteins are major part of the remains of dead animals and animal waste. Decomposers convert these proteins into urea and ammonia. Nitrifying bacteria convert the ammonia from decaying and waste matter to nitrates absorbed by plants. Lighting breaks apart nitrogen molecules in the atmosphere and the nitrogen reacts with atmospheric oxygen to form nitrogen oxides. These acids react with compounds in soil and form nitrates. Nitrates not absorbed by plants are converted by denitrifying bacteria in the soil to nitrogen gas, which is released into the atmosphere. Cause and spread of disease Infectious diseases are called pathogens. We often call pathogens microbes. Infectious diseases are those caused by pathogens that spread person to person. Salmonella is a type of food poisoning that comes from chickens. Cooking thoroughly lessens this risk substantially. HIV is a virus that causes aids. HIS is spread by body fluids. Athlete?s food is a fungal infection that thrives in warm, sweaty and moist enviornments in the skin. It can spread through contact of contaminated surfaces. Diarrheoa is produced by endotoxins that stimulate small intestine walls to contract violently and more frequently. Stopping infection Antiseptic ? stop microbes from multiplying Antibacterial ? interfere with the growth Antibiotics ? stop the multiplication Antifungal ? treat fungal infections by killing fungal cells but not human cells. ...read more.

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