Assessment 1

Question 1

What is external fertilisation?

Answer 1

Involves the fusion of gametes outside the female body. This is better suited for organisms that reproduce in aquatic environments or very moist environments.

Question 2

What is internal fertilisation?

Answer 2

Involves the fusion of gametes inside the female body e.g. mammals, birds.

Question 3

+ and - for internal fertilisation:

Answer 3

usually few eggs released
+) increased survival of the offspring: protected from predators, constant supply of nutrients, warm
+) high survival rate
-) energy - pregnancy, birth, parental care, courtship rituals

Question 4

+ and - for external fertilisation:

Answer 4

+) low energy expenditure - no pregnancy, birth or parental care
+) wide dispersal of young - decreased comp. for food and living space, allows rapid recovery in damaged areas
-) low survival rate - more predation
-) high energy expenditure to make copious amounts of gametes

Question 5

What is sexual reproduction in plants?

Answer 5

involves the meeting of gametes, which carry genetic information from both parents to the offspring

Question 6

What are the steps in plant sexual reproduction?

Answer 6

1) Pollination: the transfer of pollen from the anther to the stigma
- self-pollination (same plant) or cross-pollination (different plant of same species)
2) Fertilisation: A pollen tube germinates and grows down the style, to an ovule contained in the ovary. The fusing of the sperm with an egg to form a zygote, the egg then becomes a seed.
3) Germination: The plant embryo is dehydrated and dormant, and if the seed lands in suitable soil (water, o2, warmth) it germinates. OR
Seed dispersal: After pollination and fertilisation, seeds from inside the ovary are dispersed. The seed is carried away from the parent plant to reduce competition.

Question 7

What is asexual reproduction in plants?

Answer 7

Does not involve production of fusion of gametes, offspring is genetically identical to the parent, no mixing of genetic information to introduce variation.

Question 8

What is vegetative propagation?

Answer 8

Does not involve production or fusion of gametes, offspring is genetically identical to the parent, no mixing of genetic information to introduce variation.
- 1 parent, mitosis, no genetic variation, form of asexual reproduction

Question 9

Types of vegetative propagation:

Answer 9

• runners: modified stems that grow along the surface of soil, lateral shoot.
• suckers: modified roots that give rise to new plants, lateral root.
• tubers:
  +) fast, good at colonising new land, stable environment
  -) comp. with parent plant, no variation which is bad with disease/changing environments

Question 10

How does unicellular fungi reproduce?
- involves mitosis

Answer 10

Budding in fungi: an adult organism gives rise to a small bud, which separates from the parent and grows into a new individual
1) When environmental conditions are good, a small bud develops on the parent cell
2) As the outgrowth enlarges, the parent cell replicates its DNA, the nucleus divides and 1 copy moves into the bud
3) When the daughter cell reaches a certain size, it detaches from the parent cell and continues to grow.

Question 11

How does multicellular fungi reproduce?
- only mitosis (n)

Answer 11

Spores:
1) Sporangia produce large amounts of spores which are light, travelling long distances by wind, effectively colonising new environments.
2) Fungal spores germinate, absorbing wind through the wall, which activates the cytoplasm to grow. Nuclear divisions occur, more cytoplasm is produced, and the spore grows into a new mycelium.

Question 12

Binary fission in bacteria:
- no mitosis (because no nucleus)
- 2 genetically identical cells are produced

Answer 12

1) newly divided cell grows to twice its size
2) replicates its DNA and DNA separates
3) protein accumulates at the cleavage site
4) cytoplasm divides and a new wall is synthesised

Question 13

How do protists undergo asexual reproduction?

Answer 13

The unicellular eukaryotes undergo binary fission, and will involve mitosis.
1) newly divided cell grows to twice its size
2) replication of DNA
3) spilts into 2 cells with identical genetic material

Question 14

Similarities and difference between binary fission and budding:

Answer 14

• both binary fission and budding involve only one parent (no mate required)
• allows rapid proliferation of genetically identical organisms that are well suited in their environment
• in binary fission, DNA is replicated but not packaged into a nucleus, but this occurs in budding.
• in binary fission, both cells are equal in size because the parent cell splits in the middle. In budding, the new daughter cell is a small outgrowth from the original cells so the new daughter cell is not equal in size to the other.

Question 15

What is a hormone?

Answer 15

A chemical messenger (protein) produced by a gland and travels via the blood to target organs.
- pituitary gland regulates and controls the activity of other endocrine glands

Question 16

What are the 3 types of sex hormones in mammalian reproduction?

Answer 16

1) Androgens - ‘male’ hormone but still present in females. It controls the development and functioning of male sex hormones and secondary sex characteristics.
2) Oestrogens - ‘female’ hormone but still present in males, controls the functioning of female reproduction.
3) Progestogens - in both sexes but has greater significance in females especially in pregnancy. It is involved in pregnancy, stimulates milk production, and decreases levels that play a role in initiating menstruation.

Question 17

What hormones are in the anterior pituitary gland and their functions?

Answer 17

Follicle Stimulating Hormone (FSH): stimulates follicular growth in ovaries, stimulates oestrogen secretion.
Luteinising Hormone (LH): surge causes ovulation, results in the formation of a corpus luteum.

Question 18

What hormones are in the ovaries and their functions?

Answer 18

Oestrogen: thickens the uterine lining (endometrium), inhibits (restrain) FSH and LH for most of cycle, and stimulates FSH and release pre-ovulation.
Progesterone: thickens uterine lining (endometrium), inhibits FSH and LH

Question 19

What is Human Chorionic Gonadotropin (hCG):

Answer 19

A hormone produced by the placenta during pregnancy and stimulates corpus luteum. It helps thicken a person’s uterine lining to support a growing embryo and tells the body to stop menstruation (shed lining of uterus -> period). hCG levels rise after conception and continue to rise until 10 weeks of pregnancy.

Question 20

What is corpus luteum?

Answer 20

Secretes oestrogen (needed to grow the muscle layer of the uterus for later birth) and progesterone (needed to suppress uterine contractions during pregnancy do that the undeveloped embryo is not born prematurely). After week 12, the placenta has grown and matured enough to secrete enough oestrogen and progesterone so the corpus luteum is no longer needed.

Question 21

How do mammals increase their chances of reproductive success?

Answer 21

1) internal fertilisation - increased chance gametes meet
2) Implantation into uterine wall - increased chance of embryonic survival
3) pregnancy - protection from external environment with constant nutrient supply -> well developed young born

Question 22

What does oviparous mean?

Answer 22

‘egg-laying’ - offspring develops in eggs - usually outside parent

Question 23

What does viviparous mean?

Answer 23

‘live birth’ - animal bringing forth live young which has developed inside parent’s body

Question 24

Distinguish between a seasonal breeder and a continuous breeder:

Answer 24

Seasonal breeders are only fertile at certain periods of the year. Continuous breeders can become pregnant at any time/sexually active all year round.

Question 25

Propose a selective advantage of oestrous cycles in mammals:

Answer 25

Oestrous periods ensures young are born into favourable conditions where temp or food availability is plentiful -> increases chance of survival.

Question 26

Fertilisation in pregnancy:

Answer 26

Occurs when the haploid egg fuses with the haploid sperm, forming a diploid fertilised egg, known as a zygote. Fertilisation takes place in the fallopian tube, sperm follows egg signals and uses the temp gradient to navigate to the ovum. Following fertilisation, the egg divides by mitosis as it travels along the oviduct and begins developing into an embryo, implantation then occurs in the walls of the endometrium.