Reproduction

Question 1

Sperm acrosome

Answer 1

Membrane bound storage for enzyme that digest the layers of the ovum and allow the sperm head to penetrate

Question 2

Sperm mitochondria

Answer 2

Mitochondria is tightly packed into the middle section of the perm provide the ATP for the lashing of the tail

Question 3

Sperm nucleus

Answer 3

Contail highly dense haploid chromosome

Question 4

Sperm microtubles

Answer 4

Produce whip-like movement of the tail that keep the mature sperm in suspension and help it swim towards the ovum

Question 5

Sperm flagellum

Answer 5

Helps propel the sperm by its movement in a liquid environment

Question 6

Ovum cell surface membrane

Answer 6

Upon fertilisation with a sperm, ion channels in the membrane opne and close so that the inside of the cell becomes electrically postive

This blocks the entry of the further sperm

Question 7

Ovum Zona pellucida

Answer 7

Layer of protective jelly around the unfertilised ovum

These will combine with cortical granule upon fertilisaton to form a tough membrane to prevent other sperm from entering the ovum

Protective layer of jelly
—> forms an impermeable barrier after fertilisation to prevent otther sperm nuclei to enter the zona pellucida

Question 8

Ovum Cytoplasm

Answer 8

Cytoplasm contains nutrient for growth of the developing embryo

—> provides energy for divding zygote after fertilisation

Question 9

Ovum Nucleus

Answer 9

The haploid chromosome contains genetic material for fertilisation

Question 10

Ovum polar body

Answer 10

A small haploid cell formed at the end of the second division of meiosis. This allows for the ovum go be haploid. The polar body will not be fertilised

Question 11

Fertilisation in human process

Answer 11

1) when sperm are close to the ovum they use their flagella to swim through the follicle cells. A few huhdred sperm reach the ovum from the million that are released. The acrosome of the sperm mature along the way so that they are ready to release enzyme
2) when sperm reach the zona pellucida (jelly coat) the acrosome reaction is triggered. The enzyme stored in the head of the sperm are released and start to digest the zona pellucida
3) the membrane of the first sperm to reach the memrbanr of the ovum cell fuses with the ovum (oocytes) cell membrane and the nucleus of the sperm cell enters the cytoplasm of the ovum

Once the ovum has been fertilised a reaction called the cortical reaction occurs which causes cortical granule to harden the zona pellucida forming a tough fertilisation membrane, repelling and preventing any more sperm from entering

The sperm nucleus entering the ovum triggers meiosis 2 to occur in the egg cell. This result in three polar bodies (which are degraded) and the ha0loid ovum.

The chromosome of the male and female nuceli replicate then the cell which is now diploid and known as a zygote, start to undergo mitosis

Question 12

State two difference between sporophyte and gametophete generation

Answer 12

Sporophyte generation
—> the diploid generation in plants that produces spores by meiosis

Gametophyte
—> the haploid generation in plants that gives rise to the gametes by mitosis

Question 13

Describe a microgamete

Answer 13

A male gamete produced in plants , the pollen grains

Question 14

Describe the difference between a generative nucleus and tube nucleus

Answer 14

Generative nucleus
—> the male nucleus that will fuse with female nucleus

Tube nucleus
—> a male nucleus that will control the production of the pollen tube in fertilisation

Question 15

Define double fertilisation

Answer 15

A process that occurs in plants in which one male nucleus fuses with two polar nuclei to form the triploid endosperm nucleus and other fuses with the egg vell to form the diploid zygote

Question 16

Define external fertilisation

Answer 16

the process of fertilisation in which the female and male gamete are released outside of the parental bodies to meet and fuse in the environment

Question 17

Define internal fertilisation

Answer 17

The fertilisation of the female gamete by the male gamete whcih takes places inside the body of the female

Question 18

Define megagamete

Answer 18

The female gamete, the egg cell, in plant

Question 19

External fertilisation

Answer 19

• aquatic species
• female and male gamete discharged directly into the environemnt where they meet & fuse

DISADVANTAGES
-Wasteful

EX jellyfish
-release male & female gamete into the sea
—> a matter whether it will fertilise

Question 20

Internal fertilisation

Answer 20

-transfer of the male gamete directly to the female

EX insect
-whereby male gamete are released directly into the body of the female during mating
-this makes it keep moist environment
—> placed as close as possible

Question 21

Plant fertilisation

Answer 21

A pollen grains lands on the stigma and germinates

A pollen tube grows from the pollen grain down the style

Hydrolytic enzyme digest the style producing the tube and the digested tissue provides the nutrients for the growth of the pollen tube

The generative nucleus divide by mitosis as it travels down the style

Upon reaching the ovule one of the generative nuclei fuses with the two polar nuclei to form endosperm which is triploid and provide food for germination of the seed

The other male generative nucleus fuses with the egg cell to form a zygote which is diploid

Question 22

Define polyspermy

Answer 22

The fertilisation of an egg by more than one sperm

Question 23

Why it cant be polyspermy

Answer 23

the entry of more than two spermatozoa into the egg cytoplasm, referred to as polyspermy, causes aberrant effects on meiosis completion or embryo development and hence embryonic death, due mainly to excess male centrosomes delivered into the egg.