Every child is a new mix
Sexual reproduction creates variation.
Two sisters
Two sisters have the same parents. They share some looks, yet they are not exactly the same, and neither is exactly like a parent.
What do you think explains this?
What this lesson covers
The idea
Random mixing of chromosomes gives each offspring a unique combination, different from its parents and siblings; this variation helps some individuals adapt to changing environments, aids species survival and contributes to evolution.
Two sisters
Two sisters have the same parents. They share some looks, yet they are not exactly the same, and neither is exactly like a parent.
What do you think explains this?
- Each child gets a different mix of the parents' chromosomes
- Each child gets exactly the same chromosomes
- Each child is a clone of one parent
A new mixture
Open each tab. The chromosome colours show where each one came from.
Variation
The children got different mixtures, so each is unique. This is variation, and it matters for the survival of a species.
Random mixing of chromosomes gives each offspring a unique combination, different from its parents and siblings. This variation helps some individuals adapt to changing environments, aids species survival and contributes to evolution.
Notes
Sexual reproduction mixes chromosomes at random, so each offspring is unique. This variation helps adaptation, survival and evolution.
Check yourself
Why is a child genetically different from its parents and siblings?
What does variation help some individuals to do?
Which is an example of variation given in the book?
Over many generations, variation contributes to…
- The child is a clone of one parent. Clones come from asexual reproduction. In sexual reproduction each child gets a unique mixture.
- The random mixing of chromosomes gives each a unique combination — correct. Yes!
- The child gets no chromosomes from the parents. Each child gets chromosomes from both parents, mixed at random.
- Stop reproducing. Variation helps individuals adapt. It does not stop reproduction.
- Become identical to the others. Variation means that individuals differ from each other.
- Adapt better to changing environments — correct. Yes!
- Some people can digest milk in their adulthood — correct. Yes!
- All people have exactly the same chromosomes. Each of us receives a unique combination of chromosomes.
- Mould spores floating in air. Spores are part of asexual reproduction in moulds. They are not an example of variation among people.
- making all the individuals the same. Variation makes individuals different. Over time it contributes to evolution.
- evolution — correct. Yes!
- the loss of chromosomes. Variation comes from mixing chromosomes. It does not remove them.