3 a) reproduction

Question 1

3.1 understand the differences between sexual and asexual reproduction

Answer 1

In sexual reproduction two parents create non-identical offspring, inheriting characteristics from both parents.
In asexual reproduction a single parent creates genetically identical offspring.

Question 2

3.2 understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

Answer 2

Gametes are sex cells: the male one being sperm; the female one being an egg.
When they join together it is know as fertilisation. At this point the fused gametes become a zygote.
A the zygote then divides repeatedly, at this stage it becomes an embryo.

Question 3

3.3 describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination

Answer 3

Insect

• Brightly coloured, larger petals
• Nectar
• Scents

Wind

• Anthers stick out- past other parts of the flower
• Stamen will have large surface area.

Question 4

3.4 understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation

Answer 4

A pollen will travel down the stigma through a pollen tube, in to the ovule in the carpel. Here the pollen will fertilise the ovule, forming a zygote (the seed). The carpel (reproductive organ) becomes a fruit.

Question 5

3.5 understand that plants can reproduce asexually by natural methods (illustrated by runners) and by artificial methods (illustrated by cuttings)

Answer 5

Asexual reproduction only involves one parent, this can be achieved in two ways by plants:
Runners- eg strawberries- a second stem extend, when it reaches the ground cells specialise into root cells and a new plant develops.
Cuttings: a clipping is put in to plant hormones, encouraging the ends to become roots, when placed in soil it will then create another plant.

Question 6

3.6 describe the structure and explain the function of the male and female reproductive systems

Answer 6

Male reproductive system

• Testis- produce sperm cells, they are stored in the epididymus
• Vas deference- carries sperm to the penis
• The prostate- adds fluid to the sperm, creating semen (as does the seminal vesicles)
• The urethra- carries sperm to the end of, and out of the penis.

Female reproductive system

• Ovaries- produce eggs
• Oviducts- carry the eggs to the uterus, is the site of fertilisation
• Uterus- develops the fertilised egg on the placenta
• Cervix- entrance to uterus

Question 7

3.7 understand the roles of oestrogen and progesterone in the menstrual cycle

Answer 7

The menstrual cycle
Oestrogen and progesterone are both hormones which effect the menstrual cycle.
Oestrogen: produced in the ovaries; thickens the womb lining; prompts the release of LH.
Progesterone: produced in the corpus lutiem; maintains the lining of the womb

Question 8

3.8 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics.

Answer 8

Oestrogen- females

• The beginning of the menstrual cycle
• Body mass increases and redistributed- to hips and breasts
• Body hair- pubic
• Voice deepens slowly
• Development of sexual organs

Testosterone- males

• Production of sperm
• Growth of sexual organs
• Body hair- pubic, arms and face
• Body mass will increase, including muscle mass
• Voice breaks (becomes deeper)
• Development of a sexual drive