Aqa Biology exam b
- Created by: adina shaya
- Created on: 27-04-14 19:43
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- Biology B
- energy from respiration
- Aerobic respiration
- glucose + oxygen = carbon dioxide + water
- Most of the reactions in aerobic respiration take place inside the mitochondria
- The energy released during respiration is used to build large molecules from smaller ones and allows muscles to contract . In mammals and birds, it enables them to keep a constant temperature
- The effect of exercise on your body
- The energy released through respiration enables muscles to contract
- When you use your muscles you need more glucose and oxygen and let out more carbon dioxide
- Body responses to exercise include: an increase in heart rate. Glycegen stores are coverted to glucose for cellular respiration
- These act to increase the supply of glucose for cellular respiration
- Anaerobic respiration
- If muscles work for a long time they don't contract efficiently . They will therefore respire anaerobically.
- Anaerobic respiration is without oxygen. Glucose is incompletely broken down to form lactic acid
- The anaerobic breakdown of glucose releases less energy.
- Oxygen is needed to break down the lactic acid. The amount of oxygen needed is know as the oxygen debt
- Aerobic respiration
- Simple inheritance in animals and plants
- Cell division and growth
- In body cells chromosomes are found in pairs.
- They divide by mitosis to produce identical cells for growth, repair and replacement
- Most types of animal cells differentiate early. Many plant cells differentiate through their life.
- Cell division in sexual repoduction
- Cells in the reproductive system divide by meiosis to produce gametes
- Body cells have two chromosomes, gametes have only one
- In meiosis the gm is copied and divides twice to form four gametes, each with one set of chromosome
- Sexual reproduction gives rise to variety as gi is combined from two parents
- Stem cells
- Embryonic stem cells and adult stem cells can be made to differentiate into many different types of cell
- Stem cells have the potential to treat previously incurable conditions. we may be able to grow nerve cells or new organs.
- From Mendel to DNA
- Gregor Mendel was the first to suggest seperately inherited factors, which we call genes
- Chromosomes are made up of large molecules of DNA
- A gene is a small section of DNA that codes for a particular combination of amino acids, which make a specific protein
- Everyone has unique DNA to identify them.
- Inheritance in action
- In human cells the chromosomes determine whether you ate female (**) or male (xy)
- Some features are controlled by a single gene
- Genes can have different forms called alleles
- Some alleles are dominant and some are recessive
- We can construct genetic diagrams to predict characteristic
- Inherited conditions in humans
- Some disorders are inherited
- Polydactyly is caused by a dominant allele of a gene and can be caused by one parent
- Cystic fibrosis is caused by a rsecessive allele of a gene and so must be caused by both parents
- You can use genetic diagrams to predict how genetic disorders might be inherited or the inheritance of genetic diseases
- Stem cells and embryos
- It is important people make informed judgements about the use of embryonic stem cells in medical research and treatment
- There are a number of economic, social and ethical issues surrounding the screening of embryos
- Cell division and growth
- Old and new species
- The origins of life on earth
- Fossils are the remains of organisms from many years ago that are found in rocks
- Fossils may be formed in different ways
- Fossils give us information about organisms that lived ages ago.
- It is difficult for scientists to know how life on earth began as there is little valid evidence
- Exploring the fossil evidence
- We can learn from fossils how much or little organisms have changed
- Extinction may be caused by new predators, new diseases or new more successful competitors
- More about extinction
- Extinction can be caused by an environment change over geological time
- Mass extinctions may be caused by single catastrophic incidents like volcanoes or asteroid strikes
- Isolation and the evolution of new species
- New species arise when two populations become isolated
- In an isolated population alleles are selected that cause successful breeding
- Speciation takes place when an isolated population becomes so different from the original that successful interbreeding can no longer take place.
- The origins of life on earth
- energy from respiration
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