natural selection and human reproduction Flashcards
1
Q
what is natural selection
A
the process by which organisms with desirable genes and characteristics are favoured to pass on their genes to their offspring
2
Q
what is evolution
A
the gradual change in the inheritable characteristics of a population over time
3
Q
process of natural selection
A
- pre-existing variation
- selection pressure/force
- differential survival and reproduction
- evolutionary change
4
Q
how to structure answer regarding the process of natural selection
A
- in the population of _, there exists individuals with (variation 1) and individuals with (variation 2)
- individuals with (variation _) are less/more likely to __ because …
- individuals with (variation _) are more likely to survive and reproduce, passing on the favourable allele to their offspring
- over many generations, the population of _ will contain more individuals with (variation _)
5
Q
drivers of natural selection
A
- limited resources (food, water, shelter, mates) leading to competition between organisms
- organisms producing more offspring than the environment can support
6
Q
what is artificial selection
A
the selective breeding of species to produce offspring with desirable traits
7
Q
process of artificial selection
A
individuals with desired characteristics chosen as parents → parents bred to produce many offspring → offspring with desired characteristic are kept (and are chosen as parents), offspring without are killed or removed
8
Q
what is asexual reproduction
A
- the process that results in the production of genetically identical offspring from 1 parent, without the fusion of gametes
- arises from mitosis, a type of cell division giving rise to genetically identical cells
9
Q
advantages of asexual reproduction
A
- only 1 parent required
- fusion of gametes not required
- all beneficial qualities from parent are passed onto offspring
- fast
10
Q
disadvantages of asexual reproduction
A
- no genetic variation in offspring → species not well adapted to changes in the environment, could be easily wiped out
11
Q
what is sexual reproduction
A
- a process involving the fusion of 2 gametes to form a zygote, producing genetically dissimilar offspring
- arises from meiosis, a type of cell division that gives rise to genetically dissimilar cells
12
Q
advantages of sexual reproduction
A
- offspring may inherit beneficial qualities from both parents
- genetic variation in offspring → species more adaptable to environmental changes
13
Q
disadvantages of sexual reproduction
A
- 2 parents needed
- fusion of gametes needed
- slow
14
Q
main functions of male reproductive system
A
- produce, store, and transport sperm and the protective and nutritious fluid
- discharge sperm within the female reproductive tract
- produce and secrete male sex hormones
15
Q
external male reproductive structures
A
testes, scrotum, penis
16
Q
function of testes
A
produce testosterone, the primary male sex hormone responsible for the development of secondary sexual characteristics, and sperm
17
Q
function of scrotum
A
- keep sperm-forming cells around 2ºC cooler than body temperature which allows them to function normally and allows sperm to develop properly
- special muscles in the wall of the scrotum allow it to contract and relax, moving the testes closer to the body for warmth or further to cool the temperature
18
Q
function of penis
A
contains erectile tissue that fills with blood and causes an erection during arousal, delivers sperm to the vagina
19
Q
internal male reproductive structures
A
sperm duct/vas deferens, urethra, prostate gland
20
Q
function of sperm duct
A
delivers sperm to the urethra during ejaculation
21
Q
function of urethra
A
conveys sperm (and urine) out of the body (at different times)
22
Q
function of prostate gland
A
produces a fluid that nourishes the sperm (to stimulate them to swim actively) and provides protection from the natural acidity of the vagina
23
Q
structure of sperm
A
- head contains a large nucleus with a small amount of cytoplasm. nucleus carries a haploid set of chromosomes
- middle piece contains numerous mitochondria that provide sperm with energy to swim to the egg
- tail/flagellum allows the sperm to be motile. the beating movement of the tail enables the sperm to swim
24
Q
main functions of female reproductive system
A
- produce egg cells for reproduction
- transport ova to the site of fertilisation
- provide a safe environment for a foetus to develop
- produce female sex hormones that maintain the reproductive cycle and are responsible for the development and maintenance of secondary sexual characteristics
25
female reproductive structures
ovaries, fallopian tubes, uterus, cervix, vagina
26
function of ovaries
* site of egg production and release (ova develop in ovarian follicles surrounded by cells that nourish and protect it)
* follicles also produce oestrogen and progesterone
27
function of fallopian tubes
* site of fertilisation
* inner surface is lined with cilia that moves the egg along the oviduct toward the uterus
28
function of uterus
* site of pregnancy
* has a thick muscular wall lined with a blood-rich layer of tissue for a fetus to develop
* smooth muscle tissue in the walls contract to push the fetus out during birth
29
function of cervix
* allows the flow of menstrual blood into the vagina, directs sperms into the uterus
30
function of vagina
serves as a repository for sperm
31
structure of ovum
* abundant cytoplasm which contains a small amount of yolk
* surrounded by a cell membrane that is surrounded by another membrane which changes during fertilisation to prevent other sperm from entering the egg
32
male vs female gametes
structure:
* head, middle piece, tail vs sphere
* nucleus contains x or y chromosome vs nucleus contains x chromosome
* 60 microm long vs diameter of 120-150 microm
motility
* tail enables it to swim vs movement due to cilia in oviduct and peristalsis of oviduct wall
quantity
* millions released per ejaculation vs 1 released per month
33
stages of the menstrual cycle
menstruation, after menstruation, ovulation, after ovulation
34
what happens during menstruation
* uterine bleeding caused by the breakdown of the endometrium (and unfertilised egg)
* discharge consists of blood, clusters of cells, and mucus
35
what happens post-menstruation
* the anterior pituitary gland releases FSH which stimulates the growth of follicles in the ovary
* the developing follicles secrete oestrogen which stimulates the repair and buildup of the endometrium (+ prevents further secretion of FSH and LH)
36
what happens during ovulation
* a peak in oestrogen levels stimulates the secretion of LH
* the peak in LH stimulates ovulation
37
what happens post-ovulation
* LH stimulates the conversion of remaining follicle tissue to corpus luteum
* corpus luteum secretes progesterone and some oestrogen which continues the thickening and maintenance of the endometrium and inhibits further secretion of LH and FSH
38
what if fertilisation does not occur
falling levels of FSH and LH cause the corpus luteum to degenerate. as a result, oestrogen and progesterone decreases, the endometrium breaks down, and the menstrual cycle starts from the beginning
39
what if fertilisation occurs
* the fertilised egg becomes a zygote and then divides by mitosis to form an embryo
* the embryo secretes hCG to maintain the corpus luteum so that it can secrete progesterone to maintain the endometrium before the placenta is formed
* after 8 weeks, the placenta will start producing progesterone and the corpus luteum will degenerate
40
what is fertilisation
the process by which the nucleus of the male gamete fuses with the nucleus of the female gamete to produce a zygote
41
how does the embryo get implanted
* cilia lining the inner surface of the oviduct sweep it along the oviduct, and peristaltic movements in the wall of the oviduct also help move it to the uterus
* occurs when the embryo gets embedded in the endometrium
42
function of the placenta
* allows for the diffusion of oxygen, nutrients, and antibodies from the maternal blood to the fetal blood to occur
* allows for the diffusion of metabolic waste products from the fetal blood to the maternal blood
* produces oestrogen and progesterone
43
why are the mother’s and foetus’ blood not in direct connection?
* the mother’s blood pressure is much higher than the fetal blood pressure, difference in pressure would kill the foetus
* the blood group of the mother and foetus could be different → antibodies in mother’s blood cells would cause foetus’ blood cells to agglutinate
* pathogens and toxins within the mother’s body would not directly enter the foetus’ bloodstream
44
function of amniotic fluid
* cushions and protects the fetus (acts as a shock absorber)
* allows fetus a certain degree of movement which aids their muscular development
* maintains a constant temperature
* lubricates birth canal during childbirth
45
function of umbilical cord
* connects embryo to the embryonic villi of the placenta
* transports oxygen and nutrients to the foetus and metabolic waste products to the placenta
46
components of umbilical cord
* 2 umbilical arteries: carry deoxygenated blood containing metabolic waste products (urea, co2) from the foetus to the placenta
* 1 umbilical vein: carries oxygenated blood containing oxygen, dissolved food substances, and antibodies from the placenta to the foetus
47
what are STIs
bacterial or viral diseases transmitted through sexual intercourse from bodily fluids
48
how is HIV transmitted
* sexual intercourse
* sharing hypodermic needles
* blood transfusion
* pregnancy
49
how to prevent the transmission of HIV
* have only 1 sexual partner
* abstain from sexual intercourse
* use a condom
* do not share personal care items
* use new or sterile needles
50
what are hormones
* chemical messengers secreted in minute quantities by an endocrine gland and are transported by the bloodstream to target organs where they exert their functions
51
what are behavioural birth control methods
rhythm, abstinence
52
what are physical birth control methods
diaphragm, IUD, condom
53
what are chemical birth control methods
birth control pills, spermicide
54
what are surgical birth control methods
tubal ligation: cut and tie the oviducts
vasectomy: cut and tie the sperm ducts
55
what is IVF
* eggs are surgically removed from the ovaries after hormonal stimulation and then mixed with sperm in culture dishes for fertilisation. eggs are then incubated to allow the fertilised eggs to start developing
* embryos are then inserted into the woman’s uterus
