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Biology IGCSE > Topic 16 > Flashcards

Topic 16 Flashcards

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1
Q

Asexual reproduction

A

Process used to produce genetically identical offspring from one parent
. Example: strawberry plants using runners, tulips using bulbs and bacteria by splitting in two

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2
Q

Asexual reproduction advantages

A
  • Lots of offspring can be prodcuced very quickly
  • Less energy required
  • Offspring are genetically identical -> beneficial features will be inherited
  • Offspring reach maturity quicker
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3
Q

Asexual reproduction disadvantages

A
  • No genetic variation -> unlikely to adapt to changes in the environment
  • Overpopulation
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4
Q

Sexual reproduction

A

Process used to produce offspring that are genetically distinct from each other -> involves the fusion of the nuclei of two gametes, which are haploids (fertilisation) to form a zygote, which is diploid

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5
Q

Sexual reproduction advantages

A
  • Genetic variation -> likely to adapt to changes in the environment
  • Diversity can lead to natural selection and evolution
  • Selective breeding can be used to improve crop production and quality
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6
Q

Sexual reproduction disadvantages

A
  • Takes more time and energy than sexual reproduction
  • Two parents are needed
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7
Q

Stamen

A

Produces male gametes -> consits of anther and filament

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8
Q

Anther

A

Contains pollen grains which produce male gametes

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9
Q

Filament

A

Holds up anther

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10
Q

Petals

A

Brightly colored in insect-pollinated flowers to attract insects for pollination

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11
Q

Sepals

A

Protect flower in bud

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12
Q

Carpel

A

Produces female gametes -> consist of stigma, style and ovary

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13
Q

Stigma

A

End bit that pollen grains attatch to

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14
Q

Style

A

Supports stigma and connects it to ovary

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15
Q

Sexual reproduction in plants

A

Plants that reproduce sexually have both male and femal gametes in flower

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16
Q

Pollination

A

Transfer of pollen from an anther to a stigma

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17
Q

Self-pollination

A

Self-pollination: pollen is transferred from anther to a stigma on either same flower or a different flower on same plant
. Don’t rely on pollinators -> easier for them to spread to locations where there’s no pollinators
. Produces less variation (gene pool smaller) -> less likely to adapt to stimuli in environment

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18
Q

Cross-pollination

A

Pollen is transferred from anther to stigma on a flower from a different plant of same species
. Rely on pollinators to transfer pollen grains elsewhere -> If pollinator population declines = harder for flowers to reproduce
. Produces more variation -> more likely to adapt to stimuli in environment

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19
Q

Plant pollination: adaptations for insect pollination

A

. Large, brightly coloured petals to attract insects
. Scented flowers and nectaries (glands that secrete nectar) to attract insects
. Sticky stigma so pollen picked up by insects on other plants will stick to stigma
. Make big, sticky pollen grains which stick to insects as they go from plant to plant

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20
Q

Plant pollination: adaptations for wind pollination

A

. Small, dull petals
. No nectaries or strong scents
. Long filaments that hand anthers outside of flower so a lot of pollen fets blown away by wind
. Large and feathery stigma which hangs outside flower to catch pollen as it’s carried past by wind

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21
Q

Fertilisation in plants

A

Nucleus from pollen grain (male gamete) fuses with nucleus of female gamete in ovule -> happens in ovule

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22
Q

Steps of fertilisation in plants

A
  1. Pollen grains lands on stigma of flower -> with help from insects or wind
  2. Pollen tube grows out of a pollen grain and down through style to ovary and into ovule
  3. A nucleus from male gamete moves down tube to join with a female gamete in ovule and fertilisation occurs forming a zygote -> zygote divides by mitosis to form an embryo
  4. Each ovule containing fertilised female gamete forms a seed, which can grow into a new plant
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23
Q

Germination

A

After a seed is formed it will often lie dormant until conditions around it are right for germination (growth into a plant)
. Water: to activate enzymes that break down food reserves in seed
. Oxygen: for respiration -> transfers energy from food to growth
. Suitable temperature: for enzymes inside seed to work -> depends on type of seed

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24
Q

Urethra

A

Tube that carries sperm through penis during ejaculation and urine also passes through it to exit body

25
Q

Prostate gland

A

Produces liquid that’s added to sperm to make semen

26
Q

Penis

A

Swells when filled with blood for introducing sperm into female

27
Q

Testis

A

Where sperm is made

28
Q

Sperm duct

A

Muscular tube that carries sperm from testis towards urethra

29
Q

Scrotum

A

Hangs behind penis and contains testes

30
Q

Oviduct

A

Muscular tube that carries the ovum (egg) from ovary to uterus and where fertilisation happens

31
Q

Uterus

A

Organ where embryo geows

32
Q

Vagina

A

Where sperm are deposited

33
Q

Cervix

A

Neck of uterus

34
Q

Ovary

A

Organ that produces ova and sex hormones

35
Q

Egg cells: Energy stores in cytoplasm and Jelly coating

A

. Energy stores in cytoplasm: provide nutriens for zygote so it can divide after fertilisation to form and embryo
. Jelly coating: after fertilisation it changes structure to stop any more sperm from getting in -> make sure offspring end up woth right amount of DNA

36
Q

Sperm cells: flagellum, acrosome and mitochondria

A

. Flagellum: to swim towards egg
. Acrosome: portion in head with enzymes that digest a way through jelly coat of egg cell
. Mitochondria: provide energy for flagellum to move

37
Q

Egg VS sperm cell: size

A

Egg cell: About 0.1 mm in diameter
Sperm cell: About 0.05 mm in length

38
Q

Egg VS sperm cell: structure

A

Egg cell: spherical -> lots of cytoplasm surrounded by jelly coating
Sperm cell: Head and flagellum -> small amount of cytoplasm

39
Q

Egg VS sperm cell: mobility

A

Egg cell: don’t move independently
Sperm cell: able to move due to presence of flagellum

40
Q

Egg VS sperm cell: numbers

A

Egg cell: About 300,000 present at puberty -> released one at a time each month
Sperm cell: millions produced + released everyday

41
Q

Fertilisation

A

Fusion of nuclei from male gamete (sperm) and female gamete (egg cell)

42
Q

Pregnancy: early development

A

Zygote forms embryo (ball of cells) that implants into lining of uterus

43
Q

Pregnancy: umbilical chord

A

Carries substances between fetus and placenta

44
Q

Pregnancy: placenta

A
  • Allows dissolved nutrients and dissolved oxygen to pass into fetus’s blood from mother’s blood
  • Allows excretory products to diffuse in opposite direction
  • Provides barrier between most toxing and pathogens -> some toxins and pathogens can still enter placenta and affect fetus
45
Q

Pregnancy: aminotic fluid

A

Aminiotic sac -> contains aminiotic fluid
- Protects fetus against knocks and bumps
- Supports fetus as it grows
- Allows fetus to move

46
Q

Hormones in puberty: testosterone

A

. Extra hair on face and body
. Muscles to develop
. Penis and testes enlarge
. Sperm production
. Deepening of voice

47
Q

Hormones in puberty: oestrogen

A

. Extra hair on underarms and pubic area
. Hips to widen
. Development of breasts
. Egg release and start of periods

48
Q

Stages of the menstrual cycle

A

Stage 1: (day 1-4) menstruation starts -> uterus lining breaks down for about 4 days
Stage 2: (day 4-14) uterus lining builds up into thick spongy layer full of blood vessels + follicle (egg and its surrounding cells) matures in one of ovaries
Stage 3: (day 14) ovulation occurs -> egg released from follicle
Stage 4: (day 14-28) remains of follicle develop into corpus luteum + uterus lining is maintained -> if no fertilised egg is present and implanted the lining starts to break down and cycle starts again

49
Q

Hormones in menstrual cycle: FSH

A

. Causes follicle to mature in one of ovaries
. Stimulates ovaries to produce oestrogen

50
Q

Hormones in menstrual cycle: oestrogen

A

. Produced in ovaries
. Causes lining of uterus to grow
. Stimulates release of LH (causing release of an egg) and stops release of FSH

51
Q

Hormones in menstrual cycle: LH

A

. Stimulates release of egg from follicle (ovulation) at day 14
. Stimulates remains of follicle to develop into corpus luteum -> secretes progestrone

52
Q

Hormones in menstrual cycle: progestrone

A

. Produced in ovaries by corpus luteum after ovulation
. Prepares uterus to receive fertilised egg by mantaining uterus lining during second half of cycle -> when level of progestrone drops the uterus lining breaks down
. Stops release of FSH and LH

53
Q

Hormones in pregnancy: FSH and LH

A

Inactive durimg pregnancy

54
Q

Hormones in pregnancy: oestrogen and progestrone

A

Produced in placenta (progesterone also in smaller amount in ovaries)
- Levels stay high during pregnancy:
. To stimulate breast growth
. To mantain uterus lining
. Development of milk ducts

55
Q

STI (sexually transmitted infection)

A

Infection that is transmitted throgh sexual contact -> caused by a pathogen

56
Q

HIV (human immunodeficiency virus)

A

Pathogen that causes and STI
- Can lead to aids:
. Immune system deteriorates and eventually fails
. Vulnerable ro illness

57
Q

How can HIV spread

A

HIV is spread via bloodily fluids bith sexually and non-sexually:
. Sexual contact
. Sharing needles
. Pregnancy
. Breastfeeding
. Childbirth

58
Q

Controlling spread of STIs

A

. Education and awarness of STIs
. Abstinence -> not having sexual intercourse
. Use of condom
. Limiting number of sexual partners
. Medication

Biology IGCSE (21 decks)

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