Reproduction (B15)

IGCSE biology: Asexual reproduction (B15.1), sexual reproduction (B15.2), sexual reproduction in plants (B15.3)

What is asexual reproduction?

Process resulting in the production of genetically identical offspring from one parent

Give an example of an animal that can reproduce asexually

Starfish

Give an example of a plant that can reproduce asexually

Strawberry plants

What is binary fission?

Asexual reproduction in bacterial cells, where a single parent cell replicates its DNA and splits into two genetically identical daughter cells

What are the advantages of asexual reproduction?

Allows fast reproduction as only one parent is needed, which saves time and energy

What are the disadvantages of asexual reproduction?

All individuals will have the same characteristics, which makes the species more vulnerable to environmental changes, such as disease

What is sexual reproduction?

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

What is a zygote?

A fertilized egg cell that results from the union of a female gamete (egg/ovum) with a male gamete (sperm)

What is a haploid?

Cell containing 1 copy of every chromosome

How many haploids do humans have?

23

The nucleus of a gamete is described as the what?

Haploid

What is a diploid?

Cell containing 2 copies of every chromosome (1 as backup)

How many diploids do humans have?

46

The nucleus of a zygote is described as a what?

Diploid

What are the advantages of sexual reproduction?

Introduces variation in a population, making a species less susceptible to environmental changes such as disease

What are the disadvantages of sexual reproduction?

Much slower than asexual reproduction, as organisms spend more time and energy finding a mate

Label the parts of this insect-pollinated flower

What is the function of the sepals?

Protect the developing flower bud before it opens

What is the function of the petals?

Increase pollination efficiency

What is the function of the stamen?

Produce and disperse pollen grains

What is the function of the filament?

Providing structural support

What is the function of the anther?

Producing male gametes for fertilization, shedding pollen, and facilitating pollination

What is the function of the carpel?

Facilitate reproduction, receiving pollen, enabling fertilization, and maturing into fruit

What is the function of the stigma?

Rreceive pollen and initiate fertilization

What is the function of the style?

Pathway for the pollen tube to grow from the stigma to the ovary

What is the function of the ovary?

Protect the ovules, and develop into the fruit that contains and disperses those seeds

What is the function of the ovules?

Produce the female reproductive cells, house them for fertilization, and develop into seeds that will grow into new plant

What is pollination?

Transfer of pollen grains from the male part of the flower (anther) to the female part (stigma) to allow the plant to reproduce

What is fertilisation in plants?

The process of sexual reproduction is where male gametes combine with female gametes inside the flower to form a zygote

When does fertilization occur?

When a male gamete nucleus fuses with a nucleus in the female gamete

Describe the structural adaptations of insect-pollinated flower petals

Bright, large, and fragrant petals

Describe the structural adaptations of insect-pollinated flower colors

Bright, vibrant colors

Describe the structural adaptations of insect-pollinated flower scent

Sweet, strong scents

Describe the structural adaptations of insect-pollinated flower nectar

Sugary, energy-rich

Describe the structural adaptations of insect-pollinated flower pollen

Sticky, heavy, and often spiky or hooked

Describe the structural adaptations of insect-pollinated flower stigma

Sticky and waxy

Describe the structural adaptations of insect-pollinated flower anthers

Inside the petals on firm, short filaments, transferring sticky or spiky pollen grains

Describe the structural adaptations of wind-pollinated flower petals

Small

Describe the structural adaptations of wind-pollinated flower color

Dull, inconspicuous colors

Describe the structural adaptations of wind-pollinated flower scent

No scent :(

Describe the structural adaptations of wind-pollinated flower nectar

No nectar :(

Describe the structural adaptations of wind-pollinated flower pollen

Small, lightweight, smooth, and non-sticky

Describe the structural adaptations of wind-pollinated flower stigma

Large, feathery, often branched, that hang outside the flower petals

Describe the structural adaptations of wind-pollinated flower anthers

Large, loosely attached anthers, dangle outside the petals on long, slender filaments

Explain why insect-pollinated flowers usually have brightly coloured petals

To visually attract insects 

Explain why wind-pollinated flowers produce very large amounts of pollen

To maximize the chances of fertilization

What is germination?

The process by which a dormant seed begins to sprout and develop into a new, young plant

Why is water needed for germination?

To trigger metabolic activity and activate enzymes that turn stored food into energy for growth

Why is oxygen needed for germination?

Aerobic respiration provides ATP for the embryo to grow

Why is a suitable temperature needed for germination?

Temperature acts as the "on" switch for the internal metabolic processes required for a dormant seed to begin growing

Why would germination fail if a seed does not have enough oxygen?

Because it cannot respire, it cannot carry out aerobic respiration, being unable to provide ATP

Why might very high temperatures prevent germination?

Enzymes denature above a certain temperature, making it impossible for the seed to germinate

Describe the appearance of the anthers in wind-pollinated flowers

Large, loosely attached, and dangling outside the flower on long, slender filaments to catch the wind

Describe the appearance of the stigmas in wind-pollinated flowers

Large, feathery to capture lightweight pollen from the air

Identify the anthers and the stigmas in this wind-pollinated flower