Chapter 7 Flashcards
Biology
What are chromosomes?
long threads of DNA, found in the nucleus of every cell
How many chromosomes are there in one human body?
23 pairs, 46 chromosomes
What is DNA?
a chemical made out of long molecules with a shape like a twisted ladder
What are genes?
parts of a chromosome that determine a feature of an organism
What are the two gametes in the human body?
egg cell and sperm cell
List as many features of a sperm cell.
- has a nucleus( contains 23 chromosomes)
- has a cell surface membrane
- contains cytoplasm
- has a tail to swim vigorously/to move
- smaller than egg cells
List as many features of an egg cell.
- has a nucleus (contains 23 chromosomes)
- has a cell surface membrane
- contains cytoplasm
- contains food reserves for the zygote
- larger than sperm cells
- cannot move by themselves
What is fertilisation?
the process when an egg cell and a sperm cell fuse together
What is formed after fertilisation?
zygote
What determines the gender of a zygote?
All egg cells contain one X chromosomes. All sperm cells can contain either one X or one Y chromosome. If it is an X chromosome, the zygote will have a XX chromosome and will be a girl.. If it is a Y chromosome, the zygote will have a XY chromosome and will be a boy.
What is inheritance?
the passing of DNA from parent to offspring
What is variation?
differences between individuals that belong to the same species
What 2 factors affect variation?
DNA and enviroment
What is natural selection?
increased chance of survival of individuals that have particular advantageous features; these individuals therefore have a greater chance of survival and passing on their genes to the next generation
