Reproduction

Question 1

What is sexual reproduction?

Answer 1

Fusion of two gametes to form a zygote (fertilised egg cell)

Question 2

Gametes and Zygotes

Answer 2

Gametes are haploid as they have 23 chromosomes and Zygotes are diploid as they have 46 since eggs and sperm fuse with each other

Question 3

Advantages of Sexual reproduction

Answer 3

• Variation in offspring due to meiosis
• Better adapted to environmental changes
• Selective breeding

Question 4

Asexual Reproduction

Answer 4

The process in which one parent produces genetically identical offspring

Question 5

Advantages and disadvantages of asexual reproduction

Answer 5

• It’s relatively fast
• Genetically identical to each other
• more vulnerable to disease

Question 6

Gametes

Answer 6

These are sex cells produced by meiosis

Animals: Spem & Ovum
Plants: Pollen & Ovum

Question 7

What do gametes do?

Answer 7

They contain half the number of chromosomes compared to normal body cells.

They have adaptations to improve chances of successful fertilisation and embryo development e.g:
- Sperm cells have a tail
- Egg cells have energy stores within the cytoplasm to support early embryo development

Question 8

Fertilisation

Answer 8

The fusion of a male and female gamete to produce a zygote.
- the zygote divides by mitosis to develop an embryo and starts to become specialised to perform specific functions

Question 9

Fertilisation in humans

Answer 9

Semen is ejaculated into the female’s vagina near the cervix and sperm travel through the cervix into the uterus

Fertilisation occurs in the oviduct
Human zygote contains full 46 chromosomes

Question 10

Fertilisation in plants

Answer 10

This occurs when a pollen tube grows down from a pollen grain to deliver the male nucleus into the ovary

Question 11

Insect-Pollinated flowers

Answer 11

They are adapted to allow insects to collect pollen from one flower and easily transfer it to another

e.g
Petals - Bright colourful and large
Scent and nectar - encourage insects
Anthers - brush against insects
Stigma - sticky to catch pollen when insects brush part

Question 12

Wind Pollinated flowers

Answer 12

Adapted so wind can easily catch pollen grains and carry them to the stigmas of other flowers

Features:
Petals - small and green (no attraction)
Scent and nectar - not produced
Anthers - exposed to the wind
Stigma - feathery

Question 13

Process of fertilisation in plants

Answer 13

After successful pollination a pollen tube forms to deliver the male nucleus to the egg cell in the ovary of the flower

• The pollen tube grows down the style towards the ovary
• The pollen grain travels down the pollen tube
  Occurs when the pollen nucleus and the ovum fuse to form a zygote

Question 15

Seed and fruit formation

Answer 15

The ovule develops into a seed and the parts of the flower surrounding the ovule develop into a fruit

Question 15

Practical: Condition for germination

Answer 15

X

Question 16

Germinating seeds

Answer 16

Beginning of seed growth

• The seed contains a zygote that develops into the embryo
• During germination, the embryo grows into a seedling
• Cotyledons surround the embryo storing food for the seedling

Cotyledons provide energy until the plant can photosynthesise

Water absorption splits the seed coat, allowing the plumule and radicle to emerge

Question 17

Asexual Reproduction in Plants - runners

Answer 17

A new plant is produced when a runner touches the ground. A runner is almost like an arm off the parent plant e.g strawberries

Question 18

Asexual reproduction in plants - Cuttings

Answer 18

A piece of a plant’s stem with a few leaves if cut off the main plant. It’s then dipped in rooting gel or powder.

Question 19

Asexual reproduction in plants - bulbs

Answer 19

Some plants form bulbs. They are bases of leaves which have become swollen within the food. Buds in them develop new plants.

Question 20

Male Reproductive System

Answer 20

X

Question 21

Female Reproductive System

Answer 21

X

Question 22

The Menstrual Cycle

Answer 22

• Average menstrual cycle is 28 days long
• Ovulation occurs around day 14, with the egg travelling to the uterus
• If egg is not fertilised then menstruation begins due to the breakdown of the uterus lining
• Lasts around 5-7 days
• Lining of the uterus starts to thicken again

Question 23

Hormonal control of the menstrual cycle (Oestrogen)

Answer 23

Oestrogen levels rise from day 1 to peak just before day 14
- This causes the uterine wall to start thickening and the egg to mature
- The peak in oestrogen occurs just before the egg is released

Question 24

Hormonal control of the menstrual cycle (Progesterone)

Answer 24

Progesterone stays low from day 1-14 and starts to rise once ovulation has occurred The increasing levels cause the uterine lining to thicken even further, a fall in progesterone levels cause the uterine lining to break down

Question 25

Roles of FSH & LH in the Menstrual Cycle

Answer 25

Released from the pituitary gland FSH - causes an egg to start maturing in the ovary, also stimulates the ovaries to start releasing oestrogen LH - released when oestrogen levels have reached their peak, causes ovulation to occur and also stimulates the ovary to produce progesterone

Question 26

Interaction between all four of the menstrual cycle hormones

Answer 26

- The pituitary gland releases FSH to develop an ovarian follicle - The follicle produces an egg and oestrogen - Oestrogen stimulates uterine lining growth while inhibiting FSH production - High oestrogen levels trigger LH release causing ovulation (day 14) - Follicle becomes corpus luteum producing progesterone - Progesterone maintains uterine lining - If egg isn't fertilised, corpus luteum breaks down, progesterone levels drop, menstruation occurs - If pregnant, the corpus luteum continues producing progesterone until the placenta develops which then maintains progesterone production

Question 27

Role of the Placenta

Answer 27

The umbilical cord connects the embryo's blood supply to the placenta - It enables exchange of substances between the mother's blood and that of the fetus e.g from mother to fetus - oxygen - mineral ions and amino acids e.g fetus to mother - urea - carbon dioxide Placenta also acts as a barrier to toxins and pathogens - not nicotine and alcohol

Question 28

Amniotic Fluid

Answer 28

Amniotic fluid protects the embryo during development by cushioning it from bumps when the mother moves around

Question 29

Development of Secondary Sexual Characteristics (Female)

Answer 29

- Development of breasts - wider breasts - hair growth

Question 30

Development of Secondary Sexual Characteristics (Male)

Answer 30

- Muscles develop - Hair growth - Growth of penis Emotional changes also occur