Chapter 16.1 16.2 16.3 , Asexual Reproduction and Sexual Reproduction

Question 1

Define Asexual Reproduction

Answer 1

A process resulting in the production of genetically identical offspring from one parent.

Question 2

Name the examples of asexual reproduction

Answer 2

1. Bacteria
2. Fungi
3. Plants using asexual reproduction
   i ) Natural:
   
   • stolon
   • rhizome
   • tuber
   • bulb
     ii ) Artificial
   • cutting
   • tissue culture

Question 3

Describe asexual reproduction in Bacteria

Answer 3

Bacteria (prokaryotes; unicellular) reproduce by binary fission. This process involves the bacterium replicating its DNA and completely dividing into mother and daughter bacterium.
Each bacterium can undergo binary fission every 20 minutes so they can reproduce mass amounts very quickly.

1. Cell replicates its DNA
2. Cytoplasmic membrane elongates
3. Invaginates, cross wall forms
4. Cross wall completely forms
5. Daughter cells are produced

Question 4

Describe Asexual Reproduction in Fungi

Answer 4

Fungi (multicellular) grows long threads called hyphae on food pieces.
Two types of hyphae: feeding and reproduction
Feeding hyphae grow horizontally across.
Reproduction hyphae grow vertically above food material.
Top of hyphae is spherical bag that grows many spores (sporangium)
Will burst open at some point and release spores into the air.
If falls into favourable conditions (food water air), it germinates and grows into new identical fungus.

Question 5

Describe Asexual Reproduction of Stolons / Runners and give examples

Answer 5

Horizontal stem that grows along the surface of the ground.
Adventitious roots anchor stolons at nodes, where completely new plants are formed.
(e.g. spider plant, strawberry)

Question 6

Describe Asexual Reproduction of Rhizomes and give examples.

Answer 6

Horizontal underground stems that spread similarly to stolons
Thickened and swollen with food reserves which produce new plants form lateral buds at the nodes.
(e.g. ginger)

Question 7

Describe the asexual reproduction of tubers and bulbs, and give examples.

Answer 7

Naturally develop underground food storage organs that later develop into the following year’s plants.
(e.g. potato tubers, onion bulbs)

Question 8

Describe artificial asexual reproduction with cutting

Answer 8

Put cut end of a shoot into water or moist earth
Roots grow from the base of stem into the soil while the shoot continues to grow and produce leaves
(fast but can’t mass produce)

Question 9

Describe artificial asexual reproduction with tissue culture

Answer 9

Uses tiny pieces form the parent plant (stem cell)
Sterile agar jelly with plant hormones and lots of nutrients are needed
More expensive and difficult than cuttings
(slower but mass produce)

Question 10

pros and cons of asexual reproduction

Answer 10

Pros:
No mate is needed
No gametes needed
All good characteristics of parent is passed on to offspring
Where there is no dispersal, offspring will grow in the same favourable conditions as parent
These plants usually store large amounts of food that allow rapid growth in suitable conditions

Cons:
Little variation created, so adaption to a changing environment is unlikely
If parent is not resistant to disease, offspring won’t be resistant
No dispersal, competition for nutrients, water and light

Question 11

Define Sexual Reproduction

Answer 11

Process involving the fusion of two gametes to form a zygote and the production of offspring that are genetically different

Question 12

Define fertilization

Answer 12

Fusion of gamete nuclei

Question 13

The nuclei of gamete is _____ and the nucleus of a zygote is _____.

Answer 13

Haploid; Diploid

Question 14

Pros and Cons of Sexual Reproduction

Answer 14

Pros:
There is variation so the adaptation to a changing environment is likely, enabling survival of the species
New varieties can be created, which may have resistance to disease.
There is dispersal, reduces competition

Cons:
Two parents are usually needed (except self pollination)
growth of new plant to maturity is slow

Question 15

Name the features of a flower and their functions

Answer 15

Stamen:

• Anther: produces pollen grains
• Filament: supports anther above female reproductive organs

Carpel:

• Stigma: sticky landing site for pollen grains
• Style: tube that leads down to ovary
• Ovary: contains ovules that develop into seeds

Sepal: Protects the unopened flower
Petal: May be brightly coloured to attract insects

Question 16

Insect pollinated flowers vs Wind pollinated flowers

Answer 16

Insect:

• Petals: large and brightly coloured to attract insects
• Scent and nectar: Usually scented and with nectar to attract insects
• Number of pollen grains: Moderate - Insects transfer pollen efficiently
• Pollen: Sticky or spiky to stick to insects’ bodies
• Anthers: Inside flower, stiff and firmly attached to filaments to brush against bodies of insects
• Stigma: Inside flower, sticky - pollen grains stick to it when an insect brushes past

Wind:

• Petals: Small, often dull green or brown - no need to attract insects
• Scent and nectar: No scent or nectar
• Number of pollen grains: Large amounts because most pollen are not transferred to another flower
• Pollen grains: Smooth and light so easily carried by the wind without clumping tgt
• Anther: Outside flower, loose on long filaments to release pollen grains easily
• Stigma: Outside flower, feathery to form a network to catch drifting pollen grains

Question 17

Define pollination, self pollination and cross pollination

Answer 17

Pollination: Transfer of pollen grains from an anther to a stigma

Self pollination: Transfer of pollen grains from the anther of flower to the stigma of the same flower or different flower of same plant.

Cross pollination: Transfer of pollen grains from the anther of a flower to the stigma of the flower on a different plant of the same species.

Question 18

Name the advantages and disadvantages of self pollination

Answer 18

Pros:
No reliance on pollinators

Cons:
No variation
Cannot adapt to changing environmental conditions

Question 19

Name the advantages and disadvantages of cross-pollination

Answer 19

Pros:
Guaranteed variation
Better chance of adapting to changing conditions

Cons:
Reliance on pollinators to carry pollen to other plants

Question 20

When does fertilisation in plants occur?

Answer 20

When the pollen nucleus fuses with a nucleus of an ovule

Question 21

How does fertilisation occur in plants?

Answer 21

When a pollen grain lands on the stigma of the flower of the correct species, a pollen tube begins to grow
It grows down the style into the ovary, where it enters a small hole (the micropyle) in an ovule
The nucleus of the pollen then passes along the pollen tube and fuses with the nucleus of the ovule.

Question 21

How does fertilisation occur in plants?

Answer 21

When a pollen grain lands on the stigma of the flower of the correct species, a pollen tube begins to grow/
It grows down the style into the ovary, where it enters a small hole (the micropyle) in an ovule
The nucleus of the pollen the passes along the pollen tube and fuses with the nucleus of the ovule

Question 22

What are the main factors needed for successful germination

Answer 22

Water: Let’s the seed swell and embryo starts to grow
Oxygen: for aerobic respiration
Warmth: Increases growth rate and enzyme activity (but very high temperatures can denature the enzyme)