2. Evolution Pt3 Flashcards
What are chromosomes Made of?
DNA, contains all the genetic material.
Where are chromosomes found?
Nucleus
How many copies of one chromosomes do we have in a cell?
2 copies of every chromosomes, one pair, 2 copies of every genetic instruction
Where do our pair of chromosomes come from?
1 from the mother
1 from the dad
How many copies of a chromosomes do humans have in a cell?
46 copies, 23 pairs
What do you call a complete set of chromosomes (all 46)?
Karayotype
What must new cells contain that was the same as the old ones?
The same genetic information
What are genetically identical organisms called?
Clones
What happens in sexual reproduction?
The genetic material of 2 organisms is combined to create an offspring
What are specialised sex cells called?
Gametes
Where do you find the gametes in an animal?
The eggs and sperm
Where do you find the gametes in a plant?
The pollen and egg
Where are the gametes produced and what type of cell division do they carry out?
Gametes are produced in the testes and ovaries, they carry out meiosis
Define meiosis
Meiosis:produces 4 cells each with half the normal number of chromosomes, because only 1 chromosome from the pair remains
How many chromosomes do sperm or eggs have?
23
What happens when an egg and a sperm fuse together?
It’s called fertilisation the sperm has 23 chromosomes add the 23 from the eggs equals 46
Why is meiosis important?
It creates genetic variation, each sperm and egg has a different combination of chromosomes. Offsprings have different characteristics increasing the survival chances of the species
Does meiosis always create a genetically unique embryo?
No, the embryo can split and crest identical twins/triplet
Explain the process of meiosis
-the chromosomes double (DNA replication)
-the pair of chromosomes join up then spread, one going into one new cell and the other moving into the other cell
-then the chromosome splits forming 4 cells with 1 chromosome from each original pair
Meiosis is a cell division which produces 4 genetically unique daughter cells
How many chromosomes does meiosis produce?
Half the usual amount of chromosomes
Cells are genetically ……….. In meiosis
Different
How many cells are produced per cell division in meiosis?
4
What is the point of meiosis?
Used to produce gametes only
What cells perform meiosis?
The reproductive organs (testes and ovaries)
4 advantages of asexual reproduction
- more time & energy efficient
- only requires 1 parent
- many identical offsprings can be produced when conditions are favourable
- faster then sexual reproduction
2 disadvantages of asexual reproduction
- No genetic variation
- no evolution by natural selection, so if conditions change the whole species could go extinct
2 advantages of sexual reproduction
- produces genetic variation in offspring
- if the environment changes variation gives a survival advantage by natural selection
- natural selection can be speeded up by humans in selective breeding to increase food production
1 disadvantage of sexual reproduction
-requires 2 organisms to combine genetic material
