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Biology iGCSE > B10 - Reproduction > Flashcards

B10 - Reproduction Flashcards

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1
Q

Asexual reproduction

A

Asexual reproduction does not involve sex cells or fertilisation as only one parent is needed
* defined as a process resulting in genetically identical offspring from one parent

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2
Q

Asexual reproduction in bacteria

A

Through binary fission:
* Cell contents double so genetic material has replicated
* Cell divides into two by binary fission
* Creating two genetically identical daughter cells

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3
Q

Asexual reproduction in plants (bulbs and tubers)

A

Through budding
* A short-stemmed bulb which stores the plant’s food can induce budding
* This produces a new plant, a lateral bud which will grow and become genetically identical to the parent plant

Through tubing
* A tuber forms from swollen, fleshy underground stems
* Buds are formed from them
* Seen in potatoes

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4
Q

Asexual reproduction in plants (runners)

A
  • Plants can grow side shoots called runners that contain tiny plantlets on them
  • These will grow roots and develop into separate plants which are geneticall identical to the parent
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5
Q

Advantages of asexual reproduction (name 3)

A
  • Population can be increased rapidly when conditions are right
  • Can exploit suitable environments quickly
  • More time and energy efficient
  • Reproduction is completed much faster than sexual reproduction
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6
Q

Disadvantages of asexual reproduction (3)

A
  • Limited genetic variation in population
  • Population is vulnerable to changes in conditions and may only be suited for one habitat
  • Disease is likely to affect the whole population as there is not genetic variation
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7
Q

Sexual reproduction

A

A process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other

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8
Q

Fertilisation

A

The fusion of gamete nuclei
* resulting in genetic variation in the offspring

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9
Q

Gamete

A

A sex cell (in animals: sperm and ovum; in plants pollen nucleus and ovum)

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10
Q

Haploid nucleus

A

Have half the number of chromosomes found in other body cells
* such as gametes: 23 chromosomes
* only contain one copy from each pair of chromosomes

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11
Q

Diploid nucleus

A

The result of fusion between two haploid nuclei
* such as a zygote
* contains 46 chromosomes all in pairs

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12
Q

Zygote

A

When the male and female gametes fuse, they become a zygote which is a fertilised egg cell

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13
Q

Advantages of sexual reproduction (3)

A
  • Increases genetic variation
  • Species can adapt to new environment due to variation, giving them a survival advantage
  • Disease is less likely to affect population
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14
Q

Disadvantages of sexual reproduction (2)

A
  • Takes time and energy to find mates
  • Difficult for isolated members of the species to reproduce
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15
Q

Flowers

A

The reproductive organ of the plant
* usually contain both female and male reproductive parts

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16
Q

Pollen

A

Produces by plants and contians a haploid nucleus inside that is the male gamete
* they are not capable of locomotion (moving from one place to another

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17
Q

Pollination

A

The mechanism to transfer pollen from the anther to the stigma
* can be done by insects or by the wind

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18
Q

Flower structure

A
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19
Q

Sepal

A

Protect unopened flower

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20
Q

Petals

A

Brightly coloured in insect-pollinated flowers to attract insects

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21
Q

Anther

A

Produces and releases the male sex cell (pollen grain)

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22
Q

Stigma

A

Top of the female part of the flower which collects pollen grains

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23
Q

Ovary

A

Produces the female sex cell (ovum)

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24
Q

Ovule

A

Contains the female sex cells (found inside the ovary)

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25
Q

Petals in an insect pollinated flower

A

Large and brightly coloured to attract insects

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26
Q

Scent and nectar in an insect pollinated flower

A

Present - entices insects to visit the flower and push past stamen to get to the nectar

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27
Q

Number of pollen grains in an insect pollinated flower

A

Moderate - insects transfer pollen grains efficiently with a high chance of successful pollination

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28
Q

Size and shape of pollen grains in an insect pollinated flower

A

Larger, sticky and spiky to attach to insects and be carried away

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29
Q

Anthers in an insect pollinated flower

A

Inside flower, stiff and firmly attached to brush against insects

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30
Q

Stigma in an insect pollinated flower

A

Inside flower, sticky so pollen grains stick to it when an insect brushes past

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31
Q

Petals in a wind-pollinated flower

A

Small and dull, often green or brown in colour

32
Q

Scent and nectar in a wind-pollinated flower

A

Absent - no need to waste energy producing these as no need to attract insects

33
Q

Number of pollen grains in a wind-pollinated flower

A

Large amount - most pollen grains are not transferred to another flower si the more produced, the better chance of some successful pollination

34
Q

Shape and size of pollen grains in a wind-pollinated flower

A

Smooth, small and light so they are easily blown by the wind

35
Q

Anthers in a wind-pollinated flower

A

Outside flower, swinging loose on long filaments to release pollen grains easily

36
Q

Stigma in a wind-pollinated flower

A

Outside flower, feathery to catch drifting pollen grains

37
Q

Process of fertilisation in a plant (7 steps)

A
  1. Pollen grain lands right on the stigma (of the same species as the flower it came from)
  2. Pollen grows a pollen tube down the style towards the ovary
  3. Nucleus inside pollen grain slips down the tube
  4. The ovary contains one or more ovules which each contain an ovum with a female nucleus that the pollen can fuse with
  5. Once the nuclei fuse, a zygote is formed
  6. The zygote will start to divide and eventually form a seed within the ovule
  7. This seed will be dispersed by wind, water, gravity or other factors
38
Q

Germination

A

Germination is the start of growth in the seed

39
Q

Three factors required for successful germination (and their function)

A
  • Water: allows seed to swell up and the enzymes in the embryo to start working for growth
  • Oxygen: so that energy can be released for germination
  • Warmth: germination improves with higher temperature (up to optimum) due to enzymes
40
Q

Agents of pollination (3)

A
  • Animals, including insects
  • Wind
  • Water
41
Q

Investigation for germination (set-up)

A
  • Set up 4 boiling tubes, each containing 10 cress seeds on cotton wool
    • Tube A: dry cotton wool
    • Tube B: moist cotton wool
    • Tube C: seeds in boiled and cooled water with a layer of oil on top of it
    • Tube D: moist cotton wool
  • Leave tubes in set environment for a period of time
    • A, B and C incubated at 20 degrees
    • D in a fridge at 4 degrees
42
Q

Investigation for germination (results)

A
  • Tube A - tested for water/moisture
    • no germination
  • Tube B - tested with all factors present
    • germination took place
  • Tube C - tested for oxygen
    • no germination
  • Tube D - tested for temperature
    • no germination
43
Q

Cross-pollination

A

Occurs when the pollen from one plant is transferred to the stigma of another plant of the same species

44
Q

Self-pollination

A

Pollen from a flower can land on its own stigma or on the stigma of another flower on the same plant

45
Q

Male reproductive system

A
46
Q

Female reproductive system

A
47
Q

Prostate gland

A

Produces fluid called semen that provide sperm cells with nutrients

48
Q

Sperm duct

A

Sperm passes through the sperm duct to be mixed with fluid produced by the glands before being passed into the urethra for ejaculation

49
Q

Urethra

A

Tube running down the centre of the penis that can carry out urine or semen
* ring of muscle in the urethra prevents the urine and semen from mixing

50
Q

Testis

A

Contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone

51
Q

Scrotum

A

Sac supporting testes outside the body to ensure sperm are kept at a temperature slightly lower than body temperature

52
Q

Penis

A

Passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercourse

53
Q

Oviduct

A

Connects the ovary to the uterus and is lines with ciliated cells to push the released ovum down it
* fertilisation occurs here

54
Q

Ovary

A

Contains ova (female gamates) which will mature and develop when hormones are released

55
Q

Uterus

A

Muscular bag with a soft lining where the fertilised egg (zygote) will be implanted to develop into a foetus

56
Q

Cervix

A

Ring of muscle at the lower end of the uterus to keep the develoing foetus in place during pregnancy

57
Q

Vagina

A

Muscular tube that leads to the inside of the woman’s body
* where the male’s penis will enter during intercourse and sperm are deposited

58
Q

Adaptations (and reasons) of sperm cells (3)

A
  • Has a flagellum: enables it to swim to the egg
  • Contains enzymes in the head region (acrosome): to digest through the jelly coat and cell membrane of an egg cell
  • Contains many mitochondria: provide energy from respiration so that the flagellum can move back and forth for locomotion
59
Q

Adaptations (and reasons) of egg cells (2)

A
  • Cytoplasm containing a store of energy: provides energy for the dividing zygote after fertilisation
  • Jelly like coat: forms an impenetrable barrier after fertilisation to prevent other sperm nuclei from entering the egg cell
60
Q

Compare the size of sperm and egg

A
  • Sperm: very small (45 nano metres)
  • Egg: large (0.15 mm)
61
Q

Compare the structure of sperm and egg

A
  • Sperm: head region and flagellum, many structural adaptations
  • Egg: round cell wil few structural adaptations, covered in a jelly coat
62
Q

Compare the mobility of sperm and egg

A
  • Sperm: capable of locomotion
  • Egg: not capable of locomotion
63
Q

Compare the number of sperm and egg cells

A
  • Sperm: produced every day in huge numbers (about 100 million per day)
  • Egg: thousands of immature eggs in each ovary but only one released each month
64
Q

Describe the growth and development of the fetus (6 steps)

A
  • After fertilisation in oviduct, zygote travels towards the uterus
  • This takes about three days during which the zygote will divide several times
  • In uterus embryo embeds itself in the thick lining (implantation) and continues to grow and develop
  • Major organ development takes place in first 12 weeks during which, emrbyo gets nutrients from mother by diffusion
  • Placenta has formed, embryo called fetus
  • Gestation takes nine months, rest is growth
65
Q

Amniotic sac and fluid

A

The fetus is surrounded by an amniotic sac which contains amniotic fluid (made from the mother’s blood plasma)
* protects the fetus by cuishoning it from bumps

66
Q

Placenta

A

Allows diffusion of glucose, oxygen and amino acids from the mother’s blood to the developing foetus for growth

67
Q

Umbilical cord

A

The umbilical cord attaches the placenta to the foetus.
* It contains the umbilical artery and the umbilical vein
* The umbilical artery carries urea and carbon dioxide from the foetus to the mother’s blood.
* The umbilical vein carries oxygen and nutrients from the mother’s blood to the foetus.

68
Q

Secondary sexual characteristics

A

The changes that occur during puberty as children become adolescents
* controlled by oestrogen and testosterone

69
Q

Primary sexual characteristics

A

Present during development in the uterus
* are the differences in reproductive organs etc between males and females

70
Q

Effects of oestrogen (name 2)

A
  • Breasts develop
  • Body hair
  • Menstrual cycle begins
  • Hips get wider
71
Q

Effects of testosterone (name 3)

A
  • Growth of penis and testes
  • Growth of facial hair and body hair
  • Muscles develop
  • Voice breaks
  • Testes produce sperm
72
Q

Menstrual cycle, broken down into 3 periods of time

A

Overall, it is usually 28 days long
* Ovulation: about haflway through the cycle (day 14)
* Egg travels down the oviduct to the uterus
* Menstruation: lasts about 5-7 days and signals the beginning of the new cycle
* occurs if there’s been a failure to fertilise egg so thickenes lining breaks down
* Build up: after menstruation (at about day 7), lining starts to thicken again in preparation for the next egg

73
Q

STI

A

Unprotected sexual intercourse can lead to the transfer of pathogens via exchange of body fluids, some are STIs (sexually transmitted diseases)

74
Q

HIV

A

An example of an STI is HIV (Human Immunodeficiency Virus), the virus that usually leads to the development of acquired immunodeficiency disease (AIDS)

75
Q

How is HIV transmitted? (4)

A
  • sharing needles with an infected person
  • blood transfusion
  • sexual intercourse
  • mother to fetus through the placenta or to the baby through breastfeeding
76
Q

Ways to control the spread of STIs (name 3)

A
  • Limiting the number of sexual partners someone has
  • Not having unprotected sex (using a condom)
  • Getting tested if unprotected sex or sex with multiple partners has occurred
  • Raising awareness through education programs

Biology iGCSE (13 decks)

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