Reproduction Flashcards
Define sexual reproduction
Is where a genetic information from two organisms (Mother&Father) is combined to produce offspring which are genetically different to either parent.
What do the mother and father produce in sexual reproduction?
Gametes by meiosis - Egg and sperm cells in animals
How many chromosomes in each gametes in humans contain?
23 chromosomes - half the no. of chromosomes in a normal cell
What do the egg and sperm cell do?
Fuse together by fertilisation to form a cell with the full number of chromosomes
What do offspring inherits from both parents?
Features - receives a mixture of chromosomes from its mum and dad
What does the mixture of genetic information produce?
Variation in the offspring
Give an example of an organism that can reproduce
Flowering plants
Explain how flowering plants can reproduce
They have egg cells, but their version of sperm is known as pollen
What is required in asexual reproduction?
One parent cell - so the offspring are genetically identical to the parent
What does asexual reproduction happen by?
Mitosis - an ordinary cell makes a new cell by dividing in to 2
Define the term clone
The new cell has exactly the same genetic information as the parent cell
Give examples of organism that reproduces asexually
Bacteria
Some plants
Some animals
What do gametes have?
One copy of each chromosomes
Why do gametes only have one copy of each chromosome?
When gamete fusion takes place you get the right amount of chromosomes again - two copies of each
How do you make gametes which only have half the original number of chromosomes?
Cells divide by meiosis
What does meiosis involve?
Two cell divisions
Where does this occur in humans?
Only happens in the reproductive organs
Give examples where they occur in humans
Ovaries - Females
Testes - Males
Explain what happens in Meiosis
Duplicates DNA = two armed chromosomes
One arm of each chromosome = exact copy of other arm -Replicate
Arrange themselves into pairs
1st division - chromosome pairs line up in the centre of the cell, pairs pulled apart - new cell only has one copy of each chromosome
2nd division - chromosomes line up again in the centre of the cell. Arms of chromosomes pulled apart
= 4 gametes, single set of chromosomes
Each gamete is genetically diff. = shuffled up and at random each only gets half chromosomes
How after two gametes have fused during fertilisation?
Resulting new cell divides by mitosis to make a copy of itself
What does mitosis produce when it repeats its self many times?
Lots of new cells in an embryo
What happens as the embryo develops?
These cells then start to differentiate into the different types of specialised cell that make up a whole organism
What does the offspring from sexual reproduction have?
A mixture of two sets of chromosomes
What does the organism inherit?
Genes and features from both parents, which produces variation in the offspring
What does variation increases?
The chance of species surviving change in the environment
Explain the change in the environment that could kill some individuals
It’s likely that variation will have led to some off the offspring being able to survive in the new environment = survival advantage
Define natural selection
Individuals with characteristics that make them better adapted to the environment have a better chance of survival, they are more likely to breed successfully and pass the genes for the characteristics on.
What cab we do with selective breeding?
To speed up natural selection which allows us to produce animals with desirable characteristics
Define selective breeding
Is where individuals with a desirable characteristic are bred to produce offspring that have the desirable characteristic too.
Explain how we can increase food production
By breeding animals that produce a lot of meat
Give advantages of asexual reproduction
Needs to be one pair
Uses less energy - organisms don’t have to find a mate
Faster
Many identical offspring can be produced in favourable conditions
