Transcript of BTEC 2012 UNIT 4 (BIOLOGY) ASSIGNMENT 1 VARIATION & GENETICS
VARIATION & GENETICS the variation within a species is caused by two things
1. the genes from your parents
2. Environmental factors
some differences are just Genetic - your natural hair & eye colour
some are simply down to your environment - scars
some can be a bit of both - weight & height VARIATION environmental causes of variation Genetic causes of variation 5+7= (cc) image by anemoneprojectors on Flickr you should have a table, something like this Key Genetic words • Gamete - An egg or a sperm are called this
• Zygote - This is formed when an egg is fertilised by a sperm
• Allele - An alternative form of a gene
• Heterozygous -This word refers to a pair of chromosomes being made of two different alleles of a gene
• Homozygous - This word refers to a pair of chromosomes being made of two of the same alleles of a gene
• Dominant - This allele determines the development of a characteristic
• Recessive- This allele will determine a characteristic only if there are no dominant ones Most of your cells contain 46 Chromosomes in 23 pairs
Chromosomes are made up on Genes, you inherit one gene for each characteristic from your mother & one from your father
Genes are made up of DNA
DNA is a chemical made up of 4 bases (chemicals)
the order of the bases tells your body to make different proteins which do different jobs.
DNA is the code to make you Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell. Genes for blood group: Genes for eye colour Section of a chromosome: Where is this information stored? Genes for hair colour 25% chance of blue eyes All children have brown eyes b B b B b b B B bB bb Bb BB Bb Bb Bb Bb Offspring: Gametes: Parents: X Bb Bb X bb BB Example 1: A homozygous brown-eyed parent and a blue-eyed parent: Example 1: two heterozygous brown-eyed parents Natural selection
The theory of evolution states that evolution happens by natural selection. Here are the key points:
Individuals in a species show a wide range of variation.
This variation is because of differences in genes.
Individuals with characteristics most suited to the environment are more likely to survive and reproduce.
The genes that allowed the individuals to be successful are passed to the offspring in the next generation.
Individuals that are poorly adapted to their environment are less likely to survive and reproduce.
This means that their genes are less likely to be passed to the next generation. Given enough time, a species will gradually evolve. Mutation is a change in DNA, the hereditary material of life. An organism’s
DNA affects how it looks, how it behaves, and its physiology—all aspects
of its life. So a change in an organism’s DNA can cause changes in all aspects
of its life.
Mutations are random.
Mutations can be beneficial, neutral, or harmful for the organism, but
mutations do not “try” to supply what the organism “needs.”
The only mutations that matter to large-scale evolution are those that can
be passed on to offspring. These occur in reproductive cells like eggs and sperm
A single mutation can have a range of effects:
No change occurs in phenotype.
Some mutations don't have any noticeable effect on the phenotype of an organism.
This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function,
Small change occurs in phenotype.
A single mutation caused this cat’s ears to curl backwards slightly.
Big change occurs in phenotype.
Some really important phenotypic changes, like DDT resistance in insects are sometimes caused by single mutations. A single mutation can also have strong negative effects for the organism.
Mutations that cause the death of an organism are called lethals—and it doesn't get more negative than that.
«В этом нет необходимости», - ответил на это Беккер. Он так или иначе собирался вернуть деньги. Он поехал в Испанию не ради денег. Он сделал это из-за Сьюзан. Коммандер Тревор Стратмор - ее наставник и покровитель.