Unit 2 : Chapter 11 Flashcards
Sexual reproduction
Method of producing offspring in which an egg and sperm fuse to form a zygote
Gametes
Eggs or sperm cells
Sperm
Male gametes produced in the testes
Egg
Female gametes produced in the ovaries
Gonads
Organs in which gametes are formed; ovaries or testes
Ovaries
Egg producing organ
Testes
Male gonad that produces both sperm and male hormones`
Hermaphrodites
Has egg producing and sperm-producing organs
Chromosomes
Thread-like structure composed of DNA and protein, and visible in cells during mitosis and meiosis
Somatic cells
refers to cells of the body other than germline cells
Diploid number
refers to organisms or cells having two copies of each specific chromosome, that is, having a paired set of chromosomes
Homologous pairs
refers to members of a matching pair of chromosomes
How many cells are in a gamete
46
Haploid number
Having one copy of each specific chromosome: that is, having a set of unpaired chromosomes
Meiosis
Reduction division
Process of cell division that results in the production of new cells, each containing half the number of chromosomes of the original cell
Fertilisation
Union of egg and sperm to form a zygote
Metaphase 1
Replicated chromosomes form homologous pairs, attached to spindle fibres and lined up in the middle
Anaphase 1
Pairs of homologous chromosomes move independently to opposite ends of the cell towards poles
Independent assortment
Telophase 1
Cytoplasm begins to divide and the chromosomes are now haploid
The cells are not identical due to crossing over
Metaphase 2
Chromosomes in both cells line up on the equator, attached to spindle fibres
Anaphase 2
Sister chromatids separate and move to separate poles
Telophase 2
Chromosomes are decondensing
The nuclear membrane is reforming
Spindle fibre is breaking down
Prophase 1
Homologous pairs line up and non-sister chromatids cross over
Prophase 2
Nuclear membrane disintegrates; chromosomes become attached to spindle fibres at centromeres and move toward the centre
independent assortment
Non-homologous pairs pulled away at anaphase to create more genetic divirsity
Simultaneous hermaphrodism
Is when the species contains both egg and sperm-producing organs
Sequential hermaphrodites
When the species can change from having egg-producing organs to sperm-producing organs
Reduction division
A cell begins with 46 chromosomes reduces to gametes with 23 chromosomes
Reduction division
A cell begins with 46 chromosomes reduces to gametes with 23 chromosomes
Meiosis facts
It halves the chromosome number from 46 to 23
Produces random combinations ie; genetic divirsity
Crosses over to create new genetic combinations
Difference in mitosis and meiosis
Meiosis occurs in germ cells in ovary/testes
Meiosis is for the production of gametes, whereas mitosis is for growth and repair
Meiosis is 2 divisions, mitosis is one
Meiosis has a pair of matching chromosomes, mitosis doesn’t
Crossing over occurs in meiosis
Meiosis produces 4 haploid gametes unidentical and mitosis produces 2 identical daughter cells
Nondisjunction
When chromosomes fail to join or separate at anaphase, where there are two copies or a chromosome is missing
Advantages of sexual reproduction
Genetic diversity
Better equipped to survive a disease outbreak
Disadvantages of sexual reproduction
The energy required for the process and the finding of a suitable partner
Cannot reproduce quickly
External fertilisation
When animals release their gametes into the external environment to be fertilised outside of the female
Internal fertilisation
When males deliver sperm directly into the reproductive system of females so fertilisation occurs inside the body
