reproduction and inheritance 3.1, 3.2, 3.8, 3.9, 3.10B, 3.11, 3.12, 3.13 Flashcards
what is reproduction?
the ability of living organisms to produce offspring
sexual reproduction:
genetically varied offspring using specialised sex cells called gametes
two parent cells involved
adapts to changing environment
asexual reproduction:
genetically identical offspring
gametes are not needed, only one parent cell is involved
offspring is clones
an advantage in a stable environment
what’s the structure of a sperm cell?
have a tail-like flagellum that moves through water
males start producing sperm in puberty and continue to do so
what’s the structure of an egg cell?
female gamete
produced monthly in female humans from the ovaries
women are born with all their eggs
external fertilisation - example and explanation:
in fish, females release their ova into the water and sperm swim through the water to fertilize the ova
takes place outside ova
internal fertilisation - example and explanation:
male animals including birds and mammals, ejaculate their sperm into semen into the bodies of females during sexual intercourse
internal fertilization takes place inside the female’s body
more likely than external fertilization
once the sperm reaches the ovum, its nucleus must enter the ovum and fuse with the ovum nucleus
how do gametes and chromosomes work?
normal human body - (46 chromosomes) 23 pairs of homologous chromosomes that contain the genes
23 chromosomes from the mother’s egg cell
23 chromosomes from the father’s sperm cell
the cell has two sets of chromosomes (both maternal and paternal) - diploid cell
what type of cell is made by the fusion of the sperm and egg cells?
haploid (half) > FERTILISATION > diploid (full)
what’s the first cell that is formed at fertilization called?
zygote that contains a full set of chromosomes
what is the ovary’s role?
where egg cells are formed via meiosis in the follicle, producing hormones oestrogen and progesterone
what is the oviduct’s role?
egg cells travel down this to uterus
lined with cilia which move the cell, SITE OF FERTILISATION
what is the uterus’ role?
a lining forms in the uterus, where embryo will implant, foetus develops in the uterus which has a thick muscular wall
contracts during labour
what is the cervix’s role?
narrow opening to the uterus
dilates during labour to allow baby to be born
what is the vagina’s role?
muscular tube that leads from the cervix to the outside of the woman’s body
a man’s penis goes into the woman’s vagina during sexual intercourse and baby passes through vagina when born
what’s the testes’ role?
where sperm cells are formed by meiosis
producing hormone testosterone
what’s the sperm duct’s role?
maturing sperm are transported along this tube
what’s the role of the seminal vesicles and prostate gland?
releases liquids into the sperm duct, which mixes with the sperm to form semen
provides nutrients to the sperm
what is the role of the penis?
transports urine and semen out of the body
contains tissue which fills with blood to become erect helping pass semen out of the body and into the woman’s vagina during sexual intercourse
what’s the role of the male urethra?
a tube inside the penis that transports either urine or semen
what is the sperm’s journey?
during sexual intercourse
sperm pass along the sperm duct and are mixed with a fluid from the seminal vesicles
this mixture is called semen, is ejaculated into the vagina of the female out of the urethra
sperm then begins to swim towards oviducts
one ovum (egg cell) is released into an oviduct each month from an ovary
if ovum is present in oviducts then it may be fertilised by sperm during intercourse
random fertilisation produces genetic variation of offspring:
- each male ejaculates millions of sperm cells each of them genetically different due to the process that has created them
- each female egg will be genetically different due to how it was created
- which sperm cell that fertilises the egg is random
what is fertilisation?
the fusion of haploid male and female gametes, restoring the diploid number of chromosomes in the zygote
what’s the male’s main hormone in puberty?
testosterone
