Module 5 Heredity
Reproduction
Inquiry question: How does reproduction ensure the continuity of a species?
Explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and
asexual methods of reproduction in a variety of organisms, including but not limited to:
➔ animals: advantages of external and internal fertilisation
Fertilisation: the fusion of gametes (sperm and egg/ovum) in sexual reproduction
1. External: combination of gametes in the external environment
★ Frogs: The male frog grabs the female's back and fertilises the eggs as the female frog
releases them.
★ Bony fish: Eggs and sperm are released into the water. Sperm fuse with eggs outside of
body due to pheromones (chemical signals released by the eggs that attract sperm)
2. Internal: combination of gametes within the female body
★ Turtles: Male turtle mounts the female and aligns his cloaca with hers. The male has a penis,
which he uses to transfer sperm into the female's cloaca. (oviparous)
★ Humans: Sperm is released into the vagina where it fuses with an egg in the ampulla
(viviparous)
When fertilised internally, development can be:
1. Oviparous: External within an egg
2. Viviparous: Internal within the mother
3. Ovoviviparous: Internal within an egg within the mother
Fertilisation Advantages Disadvantages
External Large number of offspring Lots of energy & resources used
produced in the production and release of
many gametes
Reproduction can continue
without pause for gestation Zygotes/embryos are
unprotected
Offspring are dispersed, meaning
less competition No parental care=offspring may
not survive adulthood
Little energy to find a mate
Dehydration if there is not
enough water=sperm die on land
, Internal Parental care after birth Higher risk of sexually
transmitted diseases/infections
Protection of embryos> more
embryos survive to gestational Fewer offspring produced
maturity
Breeding has to be paused for
Sperm shed into a confined gestation
space, increasing the chance of
fertilisation Requires more energy to
conceive/find a mate
Less gametes produced, which
reduces energy expenditure
Characteristics Internal External Similarities
Gametes Large number of male gametes and Large numbers of gametes Male and female gametes
fewer female gametes produced produced required
Union Occurs inside the reproductive Occurs in open water Sperm fertilise the eggs when
tract of the female in organisms environments they unite
that live mostly or completely on
land
Conception Copulation: the male inserts sperm No copulation - simultaneous Sperm will fertilise eggs when
mechanism into the female’s reproductive release of gametes in very close proximity to each
tract other; gametes require a watery
environment for this to occur
Chance of fertilisation High, because male gametes are Low, because male gametes are If male and female gametes are
released into a confined space released into a large open area in close proximity to each other,
where there is more chance of where there is less chance of fertilisation will usually occur
successfully uniting with female successfully uniting with female
gametes gametes
➔ plants: asexual and sexual reproduction
Reproduction: production of offspring
1. Asexual: the production of offspring that are genetically identical to a single-parent
2. Sexual: the production of offspring that are genetically different from the two parents
Asexual reproduction in plants:
1. Fragmentation: involves new plants growing from small parts of a parent plant that fall to the
ground
, 1. Fragments of parent break or split off
2. The broken piece moves to a new location, often carried by wind or water
3. The broken piece develops roots when it lands on suitable environment
4. Roots anchor the piece, and it grows into a new plant
★ Moss
2. Using specialised reproductive structures
➢ Vegetative propagation (reproduction)→ a new plant grows from a fragment or cutting
of the parent plant or specialized reproductive structures
Type of asexual reproduction Description Examples
Stolons Stems that grow close to the
ground and develop nodes from
which new plants form on
Strawberries
Rhizomes Underground plant stems that
possess nodes capable of
generating shoots that emerge
above ground while creating root
systems for a new plant
Seagrass
Tubers Thickened part of an
underground stem that stores
nutrients. It has buds from which
new plant shoots can grow
Potato
, Bulbs Underground stem with fleshy
leaves that provide nourishment
during dormancy
Suckers Growth that develops directly
from the rootstock of a plant
Banana
Sexual reproduction in plants:
Pollination: transfer of pollen from the anther to the stigma of a plant
1. Pollen travels from the anther to the stigma of a plant
2. Once on the stigma, the tube cell germinates and creates a pollen tube that grows down the style,
carrying the generative cell that divides into two sperm cells to the ovule
3. One sperm fuses with the egg cell and the second sperm cell joins with the two polar nuclei
developing into an endosperm which becomes food for the embryo
Reproduction
Inquiry question: How does reproduction ensure the continuity of a species?
Explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and
asexual methods of reproduction in a variety of organisms, including but not limited to:
➔ animals: advantages of external and internal fertilisation
Fertilisation: the fusion of gametes (sperm and egg/ovum) in sexual reproduction
1. External: combination of gametes in the external environment
★ Frogs: The male frog grabs the female's back and fertilises the eggs as the female frog
releases them.
★ Bony fish: Eggs and sperm are released into the water. Sperm fuse with eggs outside of
body due to pheromones (chemical signals released by the eggs that attract sperm)
2. Internal: combination of gametes within the female body
★ Turtles: Male turtle mounts the female and aligns his cloaca with hers. The male has a penis,
which he uses to transfer sperm into the female's cloaca. (oviparous)
★ Humans: Sperm is released into the vagina where it fuses with an egg in the ampulla
(viviparous)
When fertilised internally, development can be:
1. Oviparous: External within an egg
2. Viviparous: Internal within the mother
3. Ovoviviparous: Internal within an egg within the mother
Fertilisation Advantages Disadvantages
External Large number of offspring Lots of energy & resources used
produced in the production and release of
many gametes
Reproduction can continue
without pause for gestation Zygotes/embryos are
unprotected
Offspring are dispersed, meaning
less competition No parental care=offspring may
not survive adulthood
Little energy to find a mate
Dehydration if there is not
enough water=sperm die on land
, Internal Parental care after birth Higher risk of sexually
transmitted diseases/infections
Protection of embryos> more
embryos survive to gestational Fewer offspring produced
maturity
Breeding has to be paused for
Sperm shed into a confined gestation
space, increasing the chance of
fertilisation Requires more energy to
conceive/find a mate
Less gametes produced, which
reduces energy expenditure
Characteristics Internal External Similarities
Gametes Large number of male gametes and Large numbers of gametes Male and female gametes
fewer female gametes produced produced required
Union Occurs inside the reproductive Occurs in open water Sperm fertilise the eggs when
tract of the female in organisms environments they unite
that live mostly or completely on
land
Conception Copulation: the male inserts sperm No copulation - simultaneous Sperm will fertilise eggs when
mechanism into the female’s reproductive release of gametes in very close proximity to each
tract other; gametes require a watery
environment for this to occur
Chance of fertilisation High, because male gametes are Low, because male gametes are If male and female gametes are
released into a confined space released into a large open area in close proximity to each other,
where there is more chance of where there is less chance of fertilisation will usually occur
successfully uniting with female successfully uniting with female
gametes gametes
➔ plants: asexual and sexual reproduction
Reproduction: production of offspring
1. Asexual: the production of offspring that are genetically identical to a single-parent
2. Sexual: the production of offspring that are genetically different from the two parents
Asexual reproduction in plants:
1. Fragmentation: involves new plants growing from small parts of a parent plant that fall to the
ground
, 1. Fragments of parent break or split off
2. The broken piece moves to a new location, often carried by wind or water
3. The broken piece develops roots when it lands on suitable environment
4. Roots anchor the piece, and it grows into a new plant
★ Moss
2. Using specialised reproductive structures
➢ Vegetative propagation (reproduction)→ a new plant grows from a fragment or cutting
of the parent plant or specialized reproductive structures
Type of asexual reproduction Description Examples
Stolons Stems that grow close to the
ground and develop nodes from
which new plants form on
Strawberries
Rhizomes Underground plant stems that
possess nodes capable of
generating shoots that emerge
above ground while creating root
systems for a new plant
Seagrass
Tubers Thickened part of an
underground stem that stores
nutrients. It has buds from which
new plant shoots can grow
Potato
, Bulbs Underground stem with fleshy
leaves that provide nourishment
during dormancy
Suckers Growth that develops directly
from the rootstock of a plant
Banana
Sexual reproduction in plants:
Pollination: transfer of pollen from the anther to the stigma of a plant
1. Pollen travels from the anther to the stigma of a plant
2. Once on the stigma, the tube cell germinates and creates a pollen tube that grows down the style,
carrying the generative cell that divides into two sperm cells to the ovule
3. One sperm fuses with the egg cell and the second sperm cell joins with the two polar nuclei
developing into an endosperm which becomes food for the embryo
