Biology Module 5.1: Reproduction
Asexual Reproduction
1. Definition: A mode of reproduction in which a new offspring
is produced by a single parent that does not involve the
fusion of gametes or change in the number of chromosomes
2. Methods of Asexual reproduction:
 Fission: A parent separates into two or more
individuals of about equal size
 Budding: A new individual develops from some
generative anatomical point of the parent organism
 Fragmentation: A type of cloning where one
organism is divided into minor fragments
 Spore formation: Gives rise to a globular structure
known as sporangia , which contains spores. The
sporangia burst to release spores and each of these
spores germinates to produce a new individual
 Vegetative reproduction: Produces progeny by any
vegetative propagule (rhizome, tubers, suckers
etc.) without gamete formation and fertilization of
male and female gametes
 Parthenogenesis: A form of reproduction in which
an egg can develop into an embryo without being
fertilized by a sperm
Advantages
Disadvantages
Efficient
Overpopulation and increased
competition for resources
Minimal time required
Due to lack of genetic variation entire
species could die off due to inability to
adapt to changes
In optimal environments
population size increases
rapidly
Sexual partner not
required
Well suited to stable
environment
Sexual Reproduction
1. Definition: The production of new living organisms by
combining genetic information from two individuals of
different sexes, the male gamete (sperm) and the female
gamete (ovum)
Advantages
Disadvantages
Fertilization is less risky and
Slower reproductive rate and
young are more likely to survive fewer offspring are produced over
a longer time period
Unfavorable genetic variation is Mates have to be found and
eliminated from population
accepted as suitable. Finding and
efficiently
competing for a mate can be risky
and energetically costly
Generates genetic variation
through recombination during
meiosis and selects for beneficial
genetic variation more
efficiently
Recombination during meiosis can
break apart beneficial genomic
combinations and introduce
deleterious variation to
populations
Able to adapt and survive
changing environmental
conditions
Potential for spread of sexually
transmitted diseases throughout
population
Improves long term evolutionary energetically costly; gamete
potential
production, mating, gestation and
rearing young requires a lot of
ongoing energy input from the
parent
Comparison between Sexual and Asexual Reproduction
Asexual
Sexual
1 Parent
2 Parents
External
Internal/External fertilized egg or
sperm
Clones of parent
Combination of parents genes
Takes place in simple and complex Complex organisms only
organisms
Less energy and time
More energy and time required
More developed at birth
Less developed at birth
Low genetic diversity
High genetic diversity
Internal fertilization of animals
1. Definition: Union of a sperm and egg cell inside the body of a
parent
2. Location: Terrestrial environments
3. Class: Mammalia (E.g. Human)
Advantages
Disadvantages
Higher chance of fertilization
Higher energy required to find a
mate
Embryo protected from predators
Less offspring produced
More likely to thrive and survive in a More energy required to raise
different environment
and care for young
External feralization of animals
1. Definition: Union of a sperm and an egg cell outside the
body of a parent, aka. spawning
2. Location: Aquatic environments
3. Class: Pisces, Amphibia (E.g. Frog)
Advantages
Disadvantages
Little energy required to mate
Many gametes go unfertilized
Large number of offspring
produced
Offspring aren't protected by
parent, therefore many die
Offspring can be spread widely
due to less competition
Classifications of animals taking part in internal fertilization
Classification Definition - Example
Placental
Fetus is nourished in the uterus and born fully
developed - Human
Marsupial
Young are born at a very early stage and continue
developing outside the uterus, usually protected by
the mother's pouch - Kangaroo
Monotreme Lay fertilized eggs covered in tough membranes,
protecting them until the young hatch - Platypus
Asexual reproduction of plants
1. Method: Natural vegetative propagation
Type
Description
Rhizome
Underground stem that
branches and gives rise to new
shoots and roots
Stolon
Shoots that grow above
ground
Tuber
Swollen underground stems
with buds that easily grow into
new plants
Bulb and Corm
Produce lateral buds that
develop into new plants
Sucker
New shoots that arise from
roots
Budding
An outgrowth of a new, plant
from the side of parent cells
Fragmentation
Broken pieces of branch
regenerate into identical ne\v
plants
Advantages
Disadvantages
Can produce a rapid increase in the Competition from sister and
number of plants growing in a
parent plants for resources
favorable area so that they
outcompete, or displace, neighboring
species
Lack of genetic variation to
protect the population against
disease or changing
environmental conditions
Sexual reproduction of plants
1. 2 Types of Plants that reproduce sexually:
 Gymnosperms: A plant of a group that comprises
those that have seeds unprotected by an ovary or
fruit, including the conifers, cycads, and ginkgo
(Non-flowering plant)
 Angiosperms: A plant of a large group that
comprises those that have flowers and produce
seeds enclosed within a carpel, including
herbaceous plants, shrubs, grasses, and most trees
(Flowering Plant)
2. Seeds of gymnosperms are produced by cones and
pollinated by wind.
3. In angiosperms, the stamen contains the sperm cells which
are then pollinated to the pistil from self-pollination or
cross-pollination. Once fertilization occurs the ovary turns
into a fruit which contains seeds.
Part
Function
Anther
Produces pollen
Filament Supports anther
Stigma
Place where pollen germinates
Style
Assists process of fertilization
Ovary
Place where ovules are produced
Petal
Attracts insects for pollination
Sepal
Encloses the developing bud
Reproduction of Fungi
1. Fungi reproduce sexually and asexually.
2. Methos of Reproduction of Fungi:
 Budding
 Spores
3. Fungi that reproduce by Budding:
 Yeast
4. Fungi that reproduce by Spores:
 Mould
 Mushrooms
 Puffballs
5. Budding: A type of asexual reproduction in which a new
organism develops from an outgrowth or bud due to cell
division at one particular site
6. Types of Reproduction by Spores:
 Mitospores: Spores produced asexually by mitosis
 Meiospores: Spores produced sexually by meiosis
Mitosis
Meiosis
Cell division where two
Cell division where four non-identical
daughter cells are produced daughter cells are produced, each with
that are identical to the
half the chromosome number of the
parent cell
parent cell
Used for growth and repair Used for production of gametes
7. When a spore lands in a suitable environment it germinates,
forming a new fungus. Spore formation and dispersal can
rapidly increase identical fungal cells, expanding and
spreading the population of a fungal species
Reproduction of Bacteria
1. Method of reproduction: Binary Fission
2. Binary Fission: A type of asexual reproduction that occurs in
prokaryote microorganisms when an organism splits into
two identical individual organisms without sex taking place
(Not Mitosis)
Reproduction of Protists
1. Methods of Reproduction:
 Binary Fission
 Budding
2. Binary Fission: For protists without a cell wall, the body of an
individual is simply pinched into two parts or halves; the
parent cell disappears and is replaced by a pair of daughter
nuclei in two new cells, although these may need to mature
to be recognizable as members of the parental species.
Binary fission can be along a transverse or longitudinal axis
or across a diameter, dividing the cytoplasm in half
3. Budding: Budding usually occurs on the outside of the cell
from which it detaches to live independently or sometimes
remains in contact to form a colony. In some species a bud
forms internally. The new nucleus is formed in a similar way
to fission but, unlike fission, the division of the cytoplasm is
unequal. At first the new organism is much smaller than the
parent.
Parts of the Mammalian Reproductive System (Female)
Structure Function
Vagina
Receives the penis during intercourse; Exit canal for
menstruation; Exit canal for child during birth
Cervix
Narrow muscular canal that connects the uterus and
vagina - dilates during birth
Uterus
Ovum is implanted in endometrium; Nurtures fertilized
egg during development until it is mature enough for
birth.
Fallopian
Tube
Connects the ovary to the uterus
Ovary
Holds egg cells and releases them during ovulation;
Produces hormones
Fimbria
Surround the ovary to catch eggs when released
Parts of the Mammalian Reproductive System (Male)
Structure
Function
Vas Deferens Tubes that lead from testes to the urethra
Penis
Deliver urine and semen to the outside of the body
Testes
Produce and store mature sperm
Fertilization
1. Definition: Fusion of two haploid gametes (egg and sperm)
to form a diploid zygote cell.
2. 4 main steps for Mammalian fertilization:
 The sperm uses enzymes from the acrosome to
dissolve and penetrate the protective layer (zona
pellucida) surrounding the egg to reach the cell
membrane
 Molecules on the sperm surface bind to receptors
(specialized proteins) on the egg's cell membrane to
ensure that a sperm of the same species fertilizes
the egg, then the nucleus of the sperm enters the
cytoplasm in the egg cell
 Changes at the surface of the egg occur to prevent
the entry of multiple sperm nuclei into the egg
 Fusion of the haploid egg and sperm nuclei results in
a diploid zygote cell
Mammalian Implantation
1. Definition: The attachment of the fertilized egg or blastocyst
to the wall of the uterus at the start of pregnancy
Mammalian Hormones associated with Birth
Hormonal Production of Females
Ovarian Cycle
Menstrual Cycle
Hormonal Control of Male Reproductive System
Role of Hormones in Pregnancy and Fetal Development
Manipulation of Reproduction in Agriculture
1. Define agriculture: The cultivation and breeding of animals,
plants and fungi for food, biofuels, fiber, timber and other
products used to sustain and enhance human life
2. Methods of Manipulation of Reproduction of Agriculture:
 Selective Breeding
 Genetic Modification
 Cloning
 Artificial Insemination
 Artificial Pollination
 IVF
Selective Breeding
1. Definition: Choosing parents with particular characteristics
to breed together and produce offspring with more
desirable characteristics
2. 4 Mains steps that apply to all forms of Selective Breeding:
 Determine the desired trait
 Interbreed parents who show the desired trait
 Select offspring with best form of the trait and
interbreed those offspring
 Continue this process until the population reliably
reproduces the desired trait
3. E.g.:
 Plants: Wheat
 Animals: Domestic Dogs
Genetic Modification
1. Definition: The deliberate altering of the genetic material of
an organism. DNA sequences will have been inserted,
removed or modified in order to introduce a new trait or
change a characteristic
2. Uses of genetic modification in plants:
 Increase crop productivity
 Provide crop resistance to insects
 Prevent disease in plants
3. Uses of genetic modification of animals:
 Improve fertility
 Improve quality and yield of meat, milk, eggs and
wool
4. E.g.:
 Plants: Corn
 Animals: Cattle
Cloning
1. Definition: The production of new individuals that contain
the same genetic information as the parent organism
2. E.g.:
 Plant: Strawberry
 Animal: Cow
Artificial Insemination
1. Definition: The medical or veterinary procedure of injecting
semen into the vagina or uterus
2. Advantages of artificial insemination:
Synchronizes pregnancies
 Bypasses fertility issues
 Improve genetics
 Mate cows to specific sires
 Reduce risk of infection and diseases
 Favorable hereditary phenotypic traits (Race-horse
breeding) Increased efficacy of livestock
3. Disadvantages of artificial insemination:
 Lack of genetic variation
4. E.g.:
 Animals: Cows

Artificial Pollination
1. Definition: Pollination carried out by humans
2. Advantages of artificial pollination:
 Controlled inheritance of favorable traits
 Self-pollination
 Successful = high yields
 Creation of new hybrid plant species
 Increased food security as a solution to global
poverty
3. Disadvantages:
 Monoculture (Loss of biodiversity)
4. E.g.:
 Plants: Kiwifruit
IVF
1. Definition: Procedure, used to overcome a range of fertility
issues, by which an egg and sperm are joined together
outside the body, in a specialized laboratory
2. Advantages:
 Favorable genes passed
 Genetic screening of embryo/sperm to avoid
disease
Multiple fertilization events, >1 can be implanted to
pose a higher chance of
 Successful pregnancies
3. Disadvantages:
 Expensive

Issues and Concerns associated with Manipulation of Reproduction
in Agriculture