Variation Flashcards
What are the two types of variation?
Genetic variation and environmental variation
Explain genetic variation
An organisms characteristics are determined by the genes inherited from their parents. These genes are passed on in sex cells (gametes)
Most animals and plants get some genes from the mother and some from the father. The combining of jeans from two parents causes genetic variation. No two of the species are genetically identical (other than identical twins)
Some characteristics are determined only by genes e.g. eye colour, blood groups and inherited disorders. For plants - violet flower colour.
Explain environmental variation
The environment that an organism lives and grows and also causes differences between members of the same species.
Any difference that has been caused by the condition something lives in, is an environmental variation.
For example plants grown on a nice sunny windowsill would grow luscious and green. The same plant grown in darkness would grow tall and spindly and its leaves would turn yellow.
Most characteristics are due to Genes AND the Environment…
Most characteristics e.g. body weight, height, skin colour, condition of teeth, academical athletic progress are determined by a mixture of genetic and environmental factors.
The maximum height of an animal or plant could grow to is determined by its genes. But whether it actually grows that all depends on its environment e.g. how much food it gets.
Most cells in your body have a nucleus. The nucleus contains…?
The nucleus contains genetic material in the form of chromosomes.
The human cell nucleus contains 23 pairs of chromosomes
Chromosomes then carry…?
Chromosomes then carry genes. Genes control the development of characteristics e.g. hair colour.
A gene is a short length of the Chromosome
What are different versions of the same gene called?
The different versions of the same genes are called alleles.
Different versions of the same gene cause different versions of the same characteristic like blue or brown eyes.
What is sexual reproduction?
Sexual reproduction is where genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to either parent.
It involves the fusion of male and female gametes
Describe the process of sexual reproduction
In sexual reproduction the mother and father produce gametes e.g. egg and sperm cells in animals
Gametes contain 23 chromosomes each. Instead of having two of each chromosome a gamete just has one of each.
The egg from the mother and the sperm cell from the father than fuse together to form a cell with the full number of chromosomes, half from the father and half from the mother
Why is there variation in offspring?
The mixture of genetic materials from both parents produces variation in the offspring.
This is why the offspring inherits features from both parents it’s received a mixture of chromosomes and chromosomes decide how you turn out.
What is a sexual reproduction?
Asexual reproduction is when an ordinary cell is divided into 2 to create a new cell that has exactly the same genetic information as the parent cell.
In a sexual reproduction there’s only one parent. There is no fusion of gametes, no mixing of chromosomes, and no genetic variation between parents and offspring. The offspring are genetically identical to the parent – they are clones.
Describe how asexual reproduction works
X shaped chromosomes have two identical halves, so each chromosome splits down the middle to form two identical sets of “half chromosomes.”
A membrane forms around each set and the DNA replicates itself to form two identical cells with complete sets of X-shaped chromosomes.
