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Reproduction in humans Flashcards

1
Q

define sexual reproduction

A

type of reproduction

involves the production of gametes by meiosis

a gamete from each parent fuses to form a zygote

genetic information from each gamete is mixed so the resulting zygote is unique

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2
Q

define the term fertilisation

A

the fusion of gamete nuclei

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3
Q

what are gametes?

A

gametes are sex cells such as sperm and eggs in animals and humans
and pollen nucleus and ovum in plants

they contain half the number of chromosomes found in other body cells so they are haploid

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4
Q

how many chromosomes do human gametes contain?

A

23

half of the normal 46 found in other body cells because they only contain one copy of each chromosomes

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5
Q

define asexual reproduction

A

type of reproduction

involves mitosis only

produces genetically identical offspring know as daughter cells

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5
Q

how do the offspring look compared to their parents when produced asexualy?

A

they are genetically identical to the parent as there is no fusion of gametes and no mixing of genetic information

resulting in clones

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5
Q

what are the advantages and disadvantages of sexual reproduction?

A

ADVANTAGES
- allows genetic variation in offspring

  • which can increase chances of survival in changing environments
  • helps in evolution
  • disease is less likely to affect offspring due to genetic variation
  • natural selection can be speeded up by humans in selective breeding to increase food production

DISADVANTAGES
- takes time and energy to find mates - two parents needed

  • difficult for isolated members of the species to reproduce
  • fewer offspring are produced as more time and energy is required
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6
Q

what are the advantages and disadvantages of asexual reproduction?

A

ADVANTAGES
- the population can be increased rapidly when conditions are right

  • can take advantages of environments quickly
  • only one parent needed
  • faster and requires less energy

DISADVANTAGES
- no genetic variation in population, offspring is identical to their parent (except from spontaneous mutations

  • The population is vulnerable to changes in conditions and may only be suited for one habitat
  • Disease is more likely to affect the whole population as there is no genetic variation
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7
Q

what is meiosis

A

form of cell division involved in the formation of gametes (non - identical haploid cells) in reproductive organs

chromosome number is halved

involves two divisions

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8
Q

what happens during the stages of meiosis?

A

chromosome pairs line up along the cell equator (centre of the cell)

the pair of chromosomes are separated and move to opposite poles of the cell

the side to which each chromosome is pulled is random - creating variation

chromosome number is halved

four unique haploid gametes are produced

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8
Q

why is meiosis important for sexual reproduction? (2)

A

increases genetic variation

it ensures that the zygote formed at fertilisation is diploid

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8
Q

describe fertilisation

A

gametes join together to have the normal number of chromosomes

the new cell then divides by mitosis (which increases the number of cells)

as the embryo develops cells differentiate

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8
Q

what is DNA?

A

the genetic material of the cell found in its nucleus

DNA is a polymer made up of two strands which form a double helix

the polymer is made up of monomers called nucleotides which each contain sugar and phosphate molecule as well as a base

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8
Q

what’s a genome?

A

the entire genetic material of an organism

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9
Q

what is a chromosome?

A

a long, coiled molecule of DNA that carries genetic information in the form of genes

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10
Q

how many chromosomes fo Human body cells have?

A

46

gametes have 23

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11
Q

define gene

A

a small section of DNA that codes for protein

each gene codes for a particular sequence of amino acids which make a specific protein

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12
Q

what are alleles?

A

different versions of the same gene

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13
Q

what is a dominant allele?

A

a version of a gene where only one copy is needed for it to be expressed

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14
Q

what is a recessive allele?

A

a version of a gene where 2 copies are needed for it to be expressed

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15
Q

what is meant when an organism is homozygous?

A

when an organism has two copies of the same allele (2 recessive of 2 dominant

16
Q

what’s heterozygous?

A

when an organism has two different versions of the same gene (one dominant and one recessive)

17
Q

what is a genotype?

A

the genes present for a trait

18
Q

what is a phenotype

A

a visible characteristic

19
what is an inherited disorder and give me an exampole of it?
a disorder caused by the inheritance of certain alleles examples cystic fibrosis - caused by a recessive allele
19
what are sex chromosomes
males have an X and a Y chromosome female have two X chromosomes
19
how do fungi usually reproduce?
by forming spores that can survive extreme conditions such as cold and lack of water. Both sexual meiotic and asexual mitotic spores may be produced, depending on the species and conditions.
20
what are the majority of genes found on the X chromosome rather than the Y chromosome?
the X chromosome is bigger than the Y so more genes are carried on it
21
what are mutation and what do they do?
Mutations may be caused by mistakes during cell division or they may be caused by exposure to DNA-damaging agents in the environment Mutations can be harmful, beneficial, or have no effect
22
What is cystic fibrosis?
A recessive phenotype caused by recessive alleles resulting in lots of mucus in the lungs, digestive system and reproductive system
22
urethra
Tube which transports urine from the bladder to the outside of the body
22
Ureter
Tube which transports urine from the kidneys to the bladder
23
Ovaries
Organs which secrete oestrogen and progesterone into the bloodstream. Eggs are produced, stored and then released from here once a month.
24
Testis
Organs which produce testosterone. Sperm are produced here.
25
Ovum
The scientific term for the female gamete.
26
Sperm
The male gamete
27
haploid and diploid
haploid a cell which has one copy of every chromosome diploid a cell that has two copies of every chromosome
27
oviduct
tube which transports egg from the ovaries to the uterus fertilisation takes place here
28
uterus
where implantation and foetal development takes place the lining of this organ is lost once a month in menstruation its contractions help to force the baby through the vigina during child birth
28
cervix
narrow gap between the vigina and the uterus diameter can dilate up to 10 cm during child birth
29
sperm duct
tube that transports sperm from the testis to the prostate gland
30
prostate gland
this gland contains a valve which controls whether urine of sperm enters urethra
31
placenta
a temporary organ is produced by the developing embryo as a site of exchange between the maternal and foetal blood it prevents the mixing of mother and foetal blood but allows diffusion of gases, nutrients and waste it also produces progesterone during pregnancy
31
average length of menstrual cycle
28 days 1 - 5 days in which menstruation takes place
32
menstruation
the breakdown and loss of the uterus lining from the vigina
33
ovulation
the process where the egg is released from the ovary
34
oestrogen
this hormone builds up thickens repairs the uterus wall after menstruation its concentrated in the blood on day 14
34
progesterone
this hormone maintains a thick lining of the uterus its levels drop at the end of the month causing menstruation to occur levels remain high during pregnancy
35
Amniotic sac
the protective bag that surrounds a developing embryo in the womb produces amniotic fluid
36
Amniotic fluid
fluid which surrounds a developing embryo it protects it from mechanical shock provides the right environment for the embryo to develop and helps maintain constant temperature
37
Umbilical cord? Umbilical artery? Umbilical vein?
The structure which joins the developing foetus to the placenta This blood vessel transports deoxygenated blood from the developing foetus to the placenta This blood vessel transports oxygenated blood from the placenta to the developing foetus
38
testosterone
hormone which controls sex drive aggression and development of the secondary sexual characteristics in males

biology (15 decks)

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