Comprehensive Study Notes: Reproduction

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Biology JAMB/WAEC/ABU Post-UTME Preparation

Table of Contents

1. Introduction and Overview

2. Asexual Reproduction

3. Sexual Reproduction in Flowering Plants

4. Reproduction in Mammals
5. Comparative Analysis

6. Practice Questions
7. Summary and Key Points

Introduction and Overview {#introduction}

Reproduction is the biological process by which organisms produce offspring, ensuring the
continuation of their species. Understanding reproduction is fundamental to biology as it
connects genetics, development, evolution, and ecology. This topic appears frequently in
Nigerian examinations, particularly in questions about life processes, genetics, and applied
biology.

Historical Context

The study of reproduction has evolved from ancient observations of plant and animal breeding
to modern molecular biology. Key milestones include Mendel's laws of inheritance, the
discovery of DNA structure, and advances in reproductive technologies. This historical
perspective helps you understand why certain concepts are emphasized in examinations.

Classification of Reproduction

Reproduction can be broadly classified into two main categories:

Asexual Reproduction: Involves a single parent producing genetically identical offspring

 Sexual Reproduction: Involves two parents contributing genetic material to produce
genetically diverse offspring

Significance in Examinations

Reproduction questions in JAMB, WAEC, and ABU Post-UTME often test your ability to
distinguish between reproductive methods, understand the advantages and disadvantages of
each, and apply this knowledge to practical situations in agriculture and medicine.

Asexual Reproduction {#asexual-reproduction}

Asexual reproduction is the process by which organisms produce offspring without the
involvement of gametes (sex cells). The offspring are genetically identical to the parent,
forming what we call clones.

Key Characteristics of Asexual Reproduction

Single parent involved

No fusion of gametes
Offspring genetically identical to parent
Usually rapid process

Less energy expenditure compared to sexual reproduction

Types of Asexual Reproduction

1. Fission (Binary Fission)

Fission is the division of a single organism into two or more parts, each capable of developing
into a complete organism. This is the primary method of reproduction in many single-celled
organisms.

Binary Fission in Paramecium: Paramecium, a unicellular protist, reproduces through binary

fission. The process occurs in several stages:

1. Nuclear Division: The macronucleus elongates and divides by constriction, while the
micronucleus divides by mitosis

2. Cytoplasmic Division: The cytoplasm begins to constrict at the center of the cell
3. Cell Separation: The cell membrane pinches inward until the cell divides into two identical
daughter cells
 4. Completion: Each daughter cell receives a complete set of organelles and nuclei

Examiner's Focus: Questions often ask about the type of nuclear division in binary fission
(mitosis, not meiosis) and why offspring are genetically identical.

Multiple Fission: Some organisms like Plasmodium (malaria parasite) undergo multiple
fission, where the nucleus divides multiple times before the cytoplasm divides, producing
many offspring simultaneously.

2. Budding

Budding is a form of asexual reproduction where a new organism develops from an outgrowth
or bud on the parent organism.

Budding in Yeast (Saccharomyces cerevisiae): Yeast cells reproduce through a process called
budding, which involves:

1. Bud Formation: A small protrusion (bud) forms on the parent cell wall
2. Nuclear Division: The parent cell's nucleus divides by mitosis
3. Nuclear Migration: One nucleus moves into the developing bud

4. Bud Growth: The bud increases in size and develops its own organelles
5. Separation: The bud eventually separates from the parent cell, becoming an independent
organism

Advantages of Budding:

Rapid reproduction under favorable conditions

No need to find a mate

Preserves successful genetic combinations
Requires less energy than sexual reproduction

Disadvantages of Budding:

Lack of genetic variation

Vulnerable to environmental changes

Population can be wiped out by single adverse factor

3. Natural Vegetative Propagation

Vegetative propagation is the production of new plants from vegetative parts (roots, stems,
leaves) of the parent plant without involving seeds.

Types of Natural Vegetative Propagation:

A. Runners (Stolons): Horizontal stems that grow along the ground surface, producing new
plants at nodes. Examples include strawberry plants and grass.

B. Rhizomes: Underground horizontal stems that produce new shoots. Examples include
ginger, turmeric, and iris plants.

C. Bulbs: Underground storage organs consisting of a short stem surrounded by fleshy leaves.
Examples include onions, garlic, and tulips.

D. Tubers: Swollen underground stems that store food and can produce new plants. Examples
include potatoes and yams.

E. Corms: Solid underground stems that store food. Examples include gladiolus and taro.

F. Fragmentation: Breaking of the parent organism into fragments, each capable of developing
into a new organism. Common in algae and some plants.

4. Artificial Vegetative Propagation

Humans have developed various techniques to propagate plants artificially for agricultural and
horticultural purposes.

A. Grafting: The process of joining parts from two plants so they grow as one. It involves:

Stock (Rootstock): The lower part with roots

Scion: The upper part that will produce the desired fruit or flowers

Types of Grafting:

1. Whip Grafting: Used when stock and scion are of similar diameter

2. Cleft Grafting: Used when stock is much larger than scion

3. Budding: A single bud is grafted onto the stock

Advantages of Grafting:

Combines desirable traits from two plants

Faster fruit production
 Disease resistance

Adaptation to different soil conditions

B. Layering: A method where roots are induced to form on a stem while it's still attached to
the parent plant.

Types of Layering:

1. Simple Layering: Bending a branch to the ground and covering part of it with soil
2. Air Layering: Wrapping moist material around a branch to encourage root formation

3. Tip Layering: Burying the tip of a branch in soil

C. Cutting: Taking a portion of a plant (stem, leaf, or root) and encouraging it to develop into a
new plant.

Factors Affecting Success of Cuttings:

Humidity levels
Temperature control
Hormone treatments (auxins)

Proper soil mixture

Timing of cutting collection

Advantages and Disadvantages of Asexual Reproduction

Advantages:

1. Speed: Rapid multiplication of organisms

2. Efficiency: No need to find mates or produce gametes

3. Energy Conservation: Less energy required than sexual reproduction

4. Genetic Preservation: Maintains successful genetic combinations
5. Colonization: Effective for rapid colonization of new habitats

Disadvantages:

1. Genetic Uniformity: Lack of genetic variation makes populations vulnerable

2. Environmental Sensitivity: Entire populations can be eliminated by single adverse factors
 3. Evolutionary Limitation: Reduced ability to adapt to changing conditions

4. Accumulation of Mutations: Harmful mutations can accumulate over generations

Applications in Agriculture

Understanding asexual reproduction is crucial for modern agriculture:

Crop Production:

Propagation of desired varieties

Maintenance of genetic purity

Rapid multiplication of improved varieties
Production of disease-free planting materials

Commercial Applications:

Tissue culture for mass propagation

Micropropagation of ornamental plants

Production of virus-free plants

Conservation of endangered species

Sexual Reproduction in Flowering Plants {#sexual-reproduction-plants}

Sexual reproduction in flowering plants (angiosperms) involves the formation of gametes,

fertilization, and the development of seeds. This process ensures genetic diversity and is
fundamental to plant evolution and adaptation.

Flower Structure and Function

A typical flower consists of four main parts, each with specific reproductive functions:

1. Sepals (Calyx)

Outermost whorl of floral parts

Usually green and leaf-like

Protect the developing flower bud
May be fused (gamosepalous) or separate (polysepalous)
2. Petals (Corolla)

Second whorl of floral parts

Often brightly colored to attract pollinators

May be fused (gamopetalous) or separate (polypetalous)

Size and color related to pollination strategy

3. Stamens (Androecium) - Male Reproductive Parts

Each stamen consists of:

Anther: Produces pollen grains (male gametes)

Filament: Stalk supporting the anther

Connective: Tissue connecting anther lobes

Anther Structure:

Contains four pollen sacs (microsporangia)

Pollen grains develop through meiosis
Mature pollen grains contain male gametes

4. Pistil/Carpel (Gynoecium) - Female Reproductive Parts

Each pistil consists of:

Stigma: Receptive surface for pollen

Style: Connects stigma to ovary
Ovary: Contains ovules (female gametes)

Ovule Structure:

Integuments: Protective layers

Nucellus: Nutritive tissue

Embryo sac: Contains egg cell and other cells

Types of Flowers Based on Reproductive Parts

1. Perfect (Bisexual) Flowers

 Contain both male and female reproductive parts

Examples: rose, hibiscus, tomato

Can potentially self-pollinate

2. Imperfect (Unisexual) Flowers

Contain either male or female parts, but not both

Staminate flowers: Only male parts (stamens)
Pistillate flowers: Only female parts (pistils)

3. Monoecious Plants

Have both male and female flowers on the same plant

Examples: corn, cucumber, oak trees

4. Dioecious Plants

Have male and female flowers on separate plants

Examples: date palm, willow, papaya

Pollination Process

Pollination is the transfer of pollen grains from the anther to the stigma. This process is
essential for sexual reproduction in flowering plants.

Types of Pollination

1. Self-Pollination (Autogamy):

Transfer of pollen from anther to stigma of the same flower

Or between flowers of the same plant

Advantages: Reliable, no dependence on external agents

Disadvantages: Reduces genetic diversity

2. Cross-Pollination (Allogamy):

Transfer of pollen between flowers of different plants

 Advantages: Increases genetic diversity, hybrid vigor

Disadvantages: Requires external agents, less reliable

Agents of Pollination

1. Wind Pollination (Anemophily):

Characteristics of wind-pollinated flowers:

Small, inconspicuous petals

Large amounts of light, dry pollen

Feathery or sticky stigmas
Exposed stamens and stigmas

Examples: grasses, corn, oak trees

2. Insect Pollination (Entomophily):

Characteristics of insect-pollinated flowers:

Brightly colored petals

Fragrant scent
Nectar production
Sticky or spiny pollen

Examples: roses, sunflowers, apple trees

3. Bird Pollination (Ornithophily):

Characteristics:

Red or orange colors

Large, sturdy flowers
Abundant nectar

No fragrance
Examples: hummingbird flowers, bottle brush

4. Water Pollination (Hydrophily):

Rare in flowering plants

 Pollen adapted for water transport

Examples: some aquatic plants

Fertilization Process

Fertilization in flowering plants involves a unique process called double fertilization, which is
characteristic of angiosperms.

Steps in Fertilization:

1. Pollen Germination:
Pollen grain lands on compatible stigma
Absorbs moisture and nutrients
Germinates to form pollen tube

2. Pollen Tube Growth:

Pollen tube grows through style toward ovary
Guided by chemical signals

Carries two male gametes

3. Double Fertilization:
First fertilization: One male gamete fuses with egg cell to form zygote (2n)

Second fertilization: Second male gamete fuses with polar nuclei to form endosperm
(3n)
4. Post-Fertilization Development:
Zygote develops into embryo

Endosperm provides nutrition for developing embryo

Ovule develops into seed
Ovary develops into fruit

Products of Sexual Reproduction

1. Seeds

Seeds are the primary products of sexual reproduction in flowering plants.

Seed Structure:
 Seed Coat (Testa): Protective outer layer

Embryo: Developing plant consisting of:

Radicle (embryonic root)
Plumule (embryonic shoot)

Cotyledons (seed leaves)

Endosperm: Nutritive tissue (may be absorbed by cotyledons)

Types of Seeds:

Monocot seeds: One cotyledon (corn, wheat)

Dicot seeds: Two cotyledons (beans, peas)

2. Fruits

Fruits develop from the ovary after fertilization and serve to protect and disperse seeds.

Types of Fruits:

A. Simple Fruits:

Develop from single flower with one pistil

Examples: apple, cherry, tomato

B. Aggregate Fruits:

Develop from single flower with multiple pistils

Examples: raspberry, blackberry

C. Multiple Fruits:

Develop from multiple flowers

Examples: pineapple, fig

Fruit Classification by Structure:

Fleshy fruits: Soft pericarp (berry, drupe, pome)

Dry fruits: Hard pericarp (nut, grain, pod)

Placentation Types
Placentation refers to the arrangement of ovules within the ovary. Understanding placentation
is important for fruit development and seed dispersal.

Types of Placentation:

1. Marginal Placentation:
Ovules attached to the margin of the ovary
Single carpel

Example: pea, bean

2. Axile Placentation:
Ovules attached to central axis

Multiple carpels
Example: tomato, orange
3. Parietal Placentation:

Ovules attached to ovary wall

Multiple carpels, but ovary appears one-chambered
Example: cucumber, passion fruit

4. Central Placentation:
Ovules attached to central column
Single chamber
Example: primrose

5. Free Central Placentation:

Ovules attached to free central column
Example: pink family plants

Advantages of Cross-Pollination

Cross-pollination provides several evolutionary advantages:

1. Genetic Diversity: Increases variation in offspring

2. Hybrid Vigor: Often results in stronger, more vigorous plants

3. Adaptation: Enhances ability to adapt to environmental changes
4. Disease Resistance: Reduces risk of widespread disease susceptibility
 5. Evolution: Provides raw material for natural selection

Mechanisms Preventing Self-Pollination

Plants have evolved various mechanisms to promote cross-pollination:

1. Dichogamy: Maturation of stamens and pistils at different times

2. Herkogamy: Physical separation of stamens and pistils

3. Self-Incompatibility: Genetic mechanisms preventing self-fertilization
4. Dioecy: Male and female flowers on separate plants

Reproduction in Mammals {#reproduction-mammals}

Mammalian reproduction involves complex anatomical structures, hormonal regulation, and

developmental processes. Understanding mammalian reproduction is crucial for questions
about human biology, livestock management, and reproductive technologies.

Male Reproductive System

The male reproductive system is designed to produce, store, and deliver sperm to the female
reproductive tract.

Primary Reproductive Organs (Gonads)

Testes:

Paired organs located in the scrotum

Primary functions: sperm production and hormone secretion

Optimal temperature: 2-3°C below body temperature

Testicular Structure:

1. Seminiferous Tubules:
Site of sperm production (spermatogenesis)
Lined with germinal epithelium

Supported by Sertoli cells

2. Interstitial Cells (Leydig Cells):
Located between seminiferous tubules
 Produce testosterone

Regulate secondary sexual characteristics

Secondary Reproductive Organs

1. Epididymis:

Coiled tube attached to each testis

Functions: sperm maturation and storage

Sperm gain motility and fertilizing capacity

2. Vas Deferens (Sperm Duct):

Muscular tube transporting sperm from epididymis

Connects to urethra via ejaculatory duct

Contains smooth muscle for sperm propulsion

3. Seminal Vesicles:

Paired glands posterior to bladder

Produce seminal fluid rich in fructose
Provides energy for sperm motility

4. Prostate Gland:

Surrounds urethra below bladder

Produces alkaline fluid
Neutralizes acidic environment of female reproductive tract

5. Cowper's Glands (Bulbourethral Glands):

Small paired glands

Produce pre-ejaculatory fluid

Neutralize residual urine acidity

Spermatogenesis

Spermatogenesis is the process of sperm production in the seminiferous tubules.

Phases of Spermatogenesis:

1. Mitotic Phase:
Spermatogonia undergo mitotic divisions

Some remain as stem cells

Others differentiate into primary spermatocytes
2. Meiotic Phase:

Primary spermatocytes undergo first meiotic division

Form secondary spermatocytes
Secondary spermatocytes undergo second meiotic division
Produce spermatids

3. Differentiation Phase (Spermiogenesis):

Spermatids transform into mature sperm
Development of flagellum, acrosome, and mitochondria

Excess cytoplasm removed

Sperm Structure:

Head: Contains nucleus and acrosome

Middle piece: Packed with mitochondria

Tail: Flagellum for motility

Duration: Complete spermatogenesis takes approximately 74 days in humans.

Female Reproductive System

The female reproductive system is more complex than the male system due to its cyclic
nature and dual function of producing gametes and supporting fetal development.

Primary Reproductive Organs

Ovaries:

Paired organs in the pelvic cavity

Functions: oocyte production and hormone secretion

Produce estrogen and progesterone

Ovarian Structure:

1. Cortex: Contains developing follicles

2. Medulla: Contains blood vessels and nerves

3. Follicles: Structures containing oocytes at various developmental stages

Secondary Reproductive Organs

1. Fallopian Tubes (Oviducts):

Paired tubes connecting ovaries to uterus

Site of fertilization

Ciliated epithelium helps transport oocyte

2. Uterus:

Hollow muscular organ

Site of implantation and fetal development

Consists of endometrium, myometrium, and perimetrium

3. Cervix:

Lower portion of uterus

Connects uterus to vagina

Produces cervical mucus

4. Vagina:

Muscular tube connecting cervix to external environment

Serves as birth canal
Receives penis during copulation

Oogenesis

Oogenesis is the process of egg cell (ovum) formation in the ovaries.

Phases of Oogenesis:

1. Multiplication Phase:
 Occurs during fetal development

Primordial germ cells multiply by mitosis

Form oogonia
2. Growth Phase:

Oogonia develop into primary oocytes

Begin first meiotic division but arrest in prophase I
Accumulate nutrients and organelles

3. Maturation Phase:
Primary oocyte completes first meiotic division
Forms secondary oocyte and first polar body
Secondary oocyte arrests in metaphase II

Completes second meiotic division only if fertilized

Key Differences from Spermatogenesis:

Oogenesis begins during fetal development

Long arrest phases in meiosis

Unequal cell division producing polar bodies
Cyclical release of oocytes

Menstrual Cycle

The menstrual cycle is a recurring physiological process in females that prepares the
reproductive system for pregnancy.

Phases of the Menstrual Cycle

1. Menstrual Phase (Days 1-5):

Shedding of endometrial lining

Low levels of estrogen and progesterone
FSH levels begin to rise

2. Follicular Phase (Days 1-13):

 Follicle development in ovary

Rising estrogen levels

Endometrial regeneration

3. Ovulation (Day 14):

Release of mature oocyte from ovary

Triggered by LH surge
Optimal time for fertilization

4. Luteal Phase (Days 15-28):

Formation of corpus luteum

High progesterone levels
Endometrial preparation for implantation

Hormonal Regulation

Hypothalamic Hormones:

GnRH (Gonadotropin-Releasing Hormone): Stimulates pituitary hormone release

Pituitary Hormones:

FSH (Follicle-Stimulating Hormone): Stimulates follicle development

LH (Luteinizing Hormone): Triggers ovulation and corpus luteum formation

Ovarian Hormones:

Estrogen: Stimulates endometrial growth, secondary sexual characteristics

Progesterone: Maintains endometrium, inhibits contractions

Fertilization and Development

Fertilization Process

Fertilization is the fusion of male and female gametes to form a zygote.

Steps in Fertilization:
 1. Sperm Capacitation:

Occurs in female reproductive tract

Sperm acquire ability to fertilize oocyte
Biochemical changes in sperm membrane

2. Sperm-Oocyte Interaction:
Sperm binds to zona pellucida
Acrosome reaction releases enzymes

Sperm penetrates zona pellucida

3. Membrane Fusion:
Sperm and oocyte membranes fuse
Prevents polyspermy

Oocyte completes second meiotic division

4. Nuclear Fusion:
Male and female pronuclei fuse

Formation of diploid zygote

First mitotic division begins

Early Development

1. Cleavage:

Rapid mitotic divisions

Cell number increases without size increase

Forms morula (16-cell stage)

2. Blastulation:

Formation of blastocyst
Inner cell mass and trophoblast differentiation
Preparation for implantation

3. Implantation:

Blastocyst attaches to endometrium

 Trophoblast invades endometrial tissue

Establishes maternal-fetal connection

4. Gastrulation:

Formation of three primary germ layers

Ectoderm, mesoderm, and endoderm

Basis for organ system development

Pregnancy and Maternal Factors

Hormonal Changes During Pregnancy

Human Chorionic Gonadotropin (hCG):

Produced by developing embryo

Maintains corpus luteum
Basis for pregnancy tests

Estrogen and Progesterone:

Maintain endometrium
Prepare mammary glands

Inhibit further ovulation

Factors Affecting Fetal Development

Maternal Nutrition:

Adequate protein, vitamins, and minerals essential

Folate prevents neural tube defects

Iron prevents anemia

Calcium supports bone development

Maternal Health:

Regular prenatal care

Management of chronic conditions
 Avoidance of teratogens

Substance Use:

Alcohol: Causes fetal alcohol syndrome

Tobacco: Reduces birth weight, increases complications

Drugs: Various developmental abnormalities

Medications: Some cause birth defects

Modern Reproductive Technologies

Assisted Reproductive Technologies (ART)

1. In Vitro Fertilization (IVF):

Fertilization occurs outside the body

Embryos cultured in laboratory
Selected embryos transferred to uterus

Process:

1. Ovarian stimulation
2. Oocyte retrieval

3. Sperm preparation
4. Fertilization in laboratory
5. Embryo culture

6. Embryo transfer

2. Intracytoplasmic Sperm Injection (ICSI):

Single sperm injected directly into oocyte

Used for severe male infertility

Higher fertilization rates

3. Gamete Intrafallopian Transfer (GIFT):

Gametes placed directly in fallopian tubes

 Fertilization occurs in natural environment

Requires at least one functional fallopian tube

Birth Control Methods

Understanding contraception is important for reproductive health and family planning.

Hormonal Methods:

Birth Control Pills: Contain estrogen and progestin

Injectable Contraceptives: Long-acting hormones
Implants: Subdermal hormone release

Patches: Transdermal hormone delivery

Barrier Methods:

Condoms: Prevent sperm entry

Diaphragms: Cover cervix

Cervical Caps: Smaller barrier devices

Intrauterine Devices (IUDs):

Copper IUDs: Toxic to sperm

Hormonal IUDs: Release progestin

Surgical Methods:

Vasectomy: Male sterilization

Tubal Ligation: Female sterilization

Natural Methods:

Rhythm Method: Timing intercourse

Withdrawal: Removal before ejaculation

Lactational Amenorrhea: Breastfeeding effect

Comparative Analysis {#comparative-analysis}

Understanding the differences and similarities between reproductive methods helps in
answering comparative questions common in examinations.

Asexual vs. Sexual Reproduction

Aspect Asexual Reproduction Sexual Reproduction

Number of parents One Two

Gamete formation No gametes Gametes involved

Genetic diversity Identical offspring Genetically diverse offspring

Speed Rapid Slower

Energy requirement Lower Higher

Environmental adaptation Limited Enhanced

Evolution potential Reduced Increased

Reproductive Strategies in Different Organisms

Bacteria:

Binary fission
Rapid reproduction
Genetic exchange through conjugation

Fungi:

Both asexual (budding, fragmentation) and sexual reproduction

Spore formation

Complex life cycles

Plants:

Alternation of generations
Both sexual and asexual reproduction

Diverse pollination strategies

Animals:
 Predominantly sexual reproduction

Complex mating behaviors

Parental care strategies

Evolutionary Significance

Advantages of Sexual Reproduction:

1. Genetic Recombination: Creates new gene combinations

2. Adaptation: Enhances survival in changing environments

3. Disease Resistance: Reduces vulnerability to pathogens

4. Elimination of Harmful Mutations: Purging of deleterious genes

Advantages of Asexual Reproduction:

1. Rapid Colonization: Quick establishment in new habitats

2. Genetic Preservation: Maintains successful combinations
3. Reproductive Assurance: No need for mates

4. Energy Efficiency: Less energy expenditure

Practice Questions {#practice-questions}

Section A: Multiple Choice Questions

1. Which of the following is NOT a characteristic of asexual reproduction? A) Single parent

involved B) Offspring genetically identical to parent C) Involves fusion of gametes D) Rapid
process

Answer: C Explanation: Asexual reproduction does not involve the fusion of gametes. This is a
characteristic of sexual reproduction.

2. In flowering plants, the male reproductive part is called: A) Pistil B) Stamen C) Sepal D)
Petal

Answer: B Explanation: The stamen is the male reproductive organ in flowers, consisting of the
anther and filament.

3. The process of sperm formation is called: A) Oogenesis B) Spermatogenesis C)

Fertilization D) Implantation
Answer: B Explanation: Spermatogenesis is the process of sperm cell development in the
seminiferous tubules of the testes.

4. Which hormone triggers ovulation in females? A) FSH B) Estrogen C) LH D) Progesterone

Answer: C Explanation: The LH (Luteinizing Hormone) surge triggers ovulation, causing the
release of the mature oocyte from the ovary.

5. Double fertilization in flowering plants results in the formation of: A) Two embryos B)
Embryo and endosperm C) Two seeds D) Seed and fruit

Answer: B Explanation: Double fertilization produces one embryo (from fusion of sperm and
egg) and endosperm (from fusion of sperm and polar nuclei).

6. The protective layer around the developing embryo is called: A) Endosperm B) Cotyledon
C) Testa D) Hilum

Answer: C Explanation: The testa is the seed coat that protects the developing embryo inside the
seed.

7. Which of the following is an example of natural vegetative propagation? A) Grafting B)

Budding (artificial) C) Runners D) Cutting

Answer: C Explanation: Runners (stolons) are natural horizontal stems that produce new plants
at nodes, like in strawberry plants.

8. The site of fertilization in mammals is typically the: A) Ovary B) Uterus C) Fallopian tube D)
Vagina

Answer: C Explanation: Fertilization usually occurs in the fallopian tubes (oviducts) where the
sperm meets the egg.

9. Which of the following prevents polyspermy? A) Acrosome reaction B) Capacitation C)

Cortical reaction D) Zona pellucida binding

Answer: C Explanation: The cortical reaction changes the zona pellucida to prevent additional
sperm from fertilizing the egg.

10. The corpus luteum is formed from: A) Graafian follicle B) Primary follicle C) Primordial
follicle D) Atretic follicle

Answer: A Explanation: Prolactin is the hormone responsible for stimulating milk production in
the mammary glands during lactation.
13. In yeast reproduction, the small outgrowth that develops into a new organism is called:
A) Spore B) Bud C) Fragment D) Gamete

Answer: B Explanation: Budding in yeast involves the formation of a small bud that grows and
eventually separates to become a new yeast cell.

14. The transfer of pollen from anther to stigma of the same flower represents: A) Cross-
pollination B) Self-pollination C) Wind pollination D) Insect pollination

Answer: B Explanation: Self-pollination (autogamy) occurs when pollen is transferred within the
same flower or between flowers of the same plant.

15. Which of the following structures develops into the fruit wall? A) Ovule B) Ovary wall C)
Style D) Stigma

Answer: B Explanation: The ovary wall (pericarp) develops into the fruit wall after fertilization,
protecting the developing seeds.

16. The phase of the menstrual cycle when the endometrium is shed is: A) Follicular phase B)
Ovulatory phase C) Luteal phase D) Menstrual phase

Answer: D Explanation: During the menstrual phase, the thickened endometrial lining is shed due
to declining hormone levels.

17. Grafting is most successful when: A) Stock and scion are from different species B) Stock
and scion are closely related C) Done during flowering season D) Performed on herbaceous
plants only

Answer: B Explanation: Grafting success increases when stock and scion are closely related
genetically, ensuring tissue compatibility.

18. The structure that nourishes the developing embryo in seeds is: A) Cotyledon B)
Endosperm C) Testa D) Hilum

Answer: B Explanation: The endosperm provides stored nutrients for the developing embryo,
formed through double fertilization.

19. Which of the following is a dioecious plant? A) Hibiscus B) Corn C) Date palm D) Rose

Answer: C Explanation: Date palms are dioecious, having male and female flowers on separate
plants, requiring both for reproduction.

20. The acrosome of sperm contains: A) Mitochondria B) Enzymes C) Genetic material D)

Nutrients
Answer: B Explanation: The acrosome contains digestive enzymes that help the sperm penetrate
the zona pellucida of the egg.

21. In tissue culture, the growth medium must contain: A) Only water and minerals B)
Hormones and nutrients C) Only carbohydrates D) Only vitamins

Answer: B Explanation: Tissue culture media require hormones (like auxins and cytokinins) along
with nutrients for proper cell division and growth.

22. The hormone that maintains the corpus luteum during early pregnancy is: A) FSH B) LH
C) hCG D) Prolactin

Answer: C Explanation: Human chorionic gonadotropin (hCG) maintains the corpus luteum,
which continues producing progesterone to support pregnancy.

23. Which type of fruit develops from a single flower with multiple pistils? A) Simple fruit B)
Aggregate fruit C) Multiple fruit D) Accessory fruit

Answer: B Explanation: Aggregate fruits like raspberries develop from a single flower containing
multiple separate pistils.

24. The process by which the blastocyst attaches to the uterine wall is: A) Fertilization B)
Cleavage C) Implantation D) Gastrulation

Answer: C Explanation: Implantation is the process where the blastocyst embeds in the
endometrial lining of the uterus.

25. Binary fission in Paramecium involves: A) Meiotic division B) Mitotic division C) Both
mitotic and meiotic division D) No nuclear division

Answer: B Explanation: Binary fission in Paramecium involves mitotic division, ensuring identical
genetic material in daughter cells.

Section B: Advanced Multiple Choice Questions

26. The phenomenon where stamens and pistils mature at different times to prevent self-
pollination is called: A) Herkogamy B) Dichogamy C) Heterostyly D) Self-incompatibility

Answer: B Explanation: Dichogamy is the temporal separation of male and female reproductive
maturity, promoting cross-pollination.

27. During spermatogenesis, the blood-testis barrier is maintained by: A) Leydig cells B)
Sertoli cells C) Spermatogonia D) Myoid cells
Answer: B Explanation: Sertoli cells form tight junctions that create the blood-testis barrier,
protecting developing sperm from immune reactions.

28. The most critical period for teratogenic effects during human development is: A) First
two weeks B) Third to eighth week C) Second trimester D) Third trimester

Answer: B Explanation: The embryonic period (weeks 3-8) is most susceptible to teratogens as
major organ systems are forming.

29. In IVF procedures, ovarian hyperstimulation is achieved using: A) Estrogen alone B)

Progesterone alone C) Gonadotropins D) GnRH antagonists only

Answer: C Explanation: Gonadotropins (FSH and LH) are used to stimulate multiple follicle
development for egg retrieval in IVF.

30. The layer of cells surrounding the mammalian egg that sperm must penetrate is: A)
Corona radiata B) Zona pellucida C) Vitelline membrane D) Cumulus oophorus

Answer: B Explanation: The zona pellucida is the glycoprotein layer that sperm must penetrate
during fertilization.

Section C: Analytical Questions

31. A farmer notices that his fruit trees produce fruit every other year. This phenomenon is
most likely due to: A) Alternate bearing caused by resource depletion B) Genetic factors C)
Soil nutrient deficiency D) Pest infestation

Answer: A Explanation: Alternate bearing occurs when trees exhaust resources producing heavy
crops, requiring a recovery year.

32. If a plant species can reproduce both sexually and asexually, under what conditions
would asexual reproduction be favored? A) When genetic diversity is needed B) In stable,
favorable environments C) During periods of environmental stress D) When pollinators are
abundant

Answer: B Explanation: Asexual reproduction is advantageous in stable environments where the

parent genotype is well-adapted.

33. The success rate of grafting decreases as the taxonomic distance between stock and
scion increases because: A) Physical incompatibility B) Genetic incompatibility affecting
tissue fusion C) Different growth rates D) Seasonal differences

Answer: B Explanation: Greater genetic distance leads to tissue incompatibility, rejection

responses, and poor vascular connection.
34. In populations reproducing primarily through parthenogenesis, what would be the
primary evolutionary disadvantage? A) Slow reproduction rate B) High energy costs C)
Reduced genetic variation D) Complex mating behaviors

Answer: C Explanation: Parthenogenesis produces genetically identical offspring, reducing

variation needed for adaptation.

35. The timing of ovulation in relation to the menstrual cycle is crucial for fertility because:
A) Hormonal levels are optimal B) The egg has a limited lifespan C) Cervical mucus is most
receptive D) All of the above

Answer: D Explanation: Ovulation timing is critical due to the short egg lifespan, optimal
hormone levels, and favorable cervical conditions.

Section D: Application Questions

36. A gardener wants to propagate a rare flowering plant that produces few viable seeds. The
best asexual propagation method would be: A) Seed collection B) Tissue culture C) Natural
fragmentation D) Waiting for natural runners

Answer: B Explanation: Tissue culture allows rapid multiplication of rare plants from small tissue
samples when seeds are scarce.

37. In agricultural production, F1 hybrid seeds are preferred because they: A) Are easier to
produce B) Show hybrid vigor C) Can be saved for next season D) Require less care

Answer: B Explanation: F1 hybrids often display hybrid vigor (heterosis), showing superior traits
compared to parents.

38. A couple has been trying to conceive for two years. The woman has regular menstrual
cycles but ultrasound shows blocked fallopian tubes. The most appropriate treatment would
be: A) Hormone therapy B) Surgery to clear tubes C) IVF D) Artificial insemination

Answer: C Explanation: IVF bypasses blocked fallopian tubes by performing fertilization outside
the body.

39. An orchard owner wants to combine disease resistance from one variety with fruit quality
from another. The best approach is: A) Cross-breeding B) Grafting C) Tissue culture D)
Selection breeding

Answer: B Explanation: Grafting allows combination of desirable traits from two varieties on a
single plant.
40. To prevent inbreeding depression in a small plant population, a botanist should: A)
Increase asexual reproduction B) Promote self-pollination C) Introduce genetic diversity
through cross-pollination D) Reduce population size further

Answer: C Explanation: Cross-pollination with genetically diverse individuals reduces inbreeding

and maintains genetic health.

Section E: Advanced Application Questions

41. A plant breeder working with wind-pollinated crops would focus on: A) Flower color and
fragrance B) Nectar production C) Pollen production and dispersal D) Flower size

Answer: C Explanation: Wind-pollinated plants require abundant, lightweight pollen for effective
dispersal without animal vectors.

42. In assisted reproductive technology, pre-implantation genetic diagnosis (PGD) is used to:
A) Enhance fertilization rates B) Select healthy embryos C) Stimulate ovulation D) Improve
sperm quality

Answer: B Explanation: PGD screens embryos for genetic disorders before implantation, allowing
selection of healthy embryos.

43. The discovery that mammalian eggs can remain viable for only 12-24 hours after
ovulation has implications for: A) Fertility treatments timing B) Natural family planning C)
Understanding reproductive windows D) All of the above

Answer: D Explanation: The short egg viability period affects timing strategies for both
conception and contraception methods.

44. Polyembryony in citrus fruits results from: A) Multiple fertilization events B) Nucellar
embryony C) Parthenogenesis D) Apomixis

Answer: B Explanation: Nucellar embryony produces multiple embryos from nucellar tissue
without fertilization in citrus.

45. The effectiveness of the rhythm method of birth control depends on: A) Accurate tracking
of ovulation B) Regular menstrual cycles C) Understanding fertility signs D) All of the above

Answer: D Explanation: Natural family planning requires regular cycles, accurate ovulation
tracking, and recognition of fertility indicators.

Section F: Synthesis Questions

46. Compare the energy investment in sexual versus asexual reproduction and explain why
both strategies persist in nature:

Model Answer: Sexual reproduction requires higher energy investment due to gamete
production, mate finding, courtship behaviors, and the genetic cost of producing males who
don't directly contribute offspring. However, it persists because it generates genetic diversity
that enhances adaptation to changing environments, provides resistance to pathogens, and
allows elimination of harmful mutations.

Asexual reproduction requires lower energy investment and allows rapid population growth in
stable environments. It preserves successful genetic combinations and ensures reproductive
success without mate dependency. Both strategies persist because they are advantageous
under different environmental conditions and life history strategies.

47. Explain why double fertilization in angiosperms is considered an evolutionary advantage:

Model Answer: Double fertilization is advantageous because it ensures efficient resource

allocation. The endosperm develops only when fertilization occurs, preventing wasteful
nutrient investment in unfertilized ovules. The triploid endosperm provides optimal nutrition
for embryo development. This mechanism also allows for parent-offspring conflict resolution
through genomic imprinting and provides flexibility in seed provisioning based on
environmental conditions.

48. Analyze the factors that would influence the choice of contraceptive method for different
populations:

Model Answer: Contraceptive choice depends on multiple factors including effectiveness

requirements, health considerations, cultural acceptability, cost, accessibility, and reversibility
needs. Hormonal methods offer high effectiveness but may have health contraindications.
Barrier methods have fewer side effects but require consistent use. Long-acting methods suit
populations with limited healthcare access. Cultural and religious factors influence
acceptance of different methods. Economic factors determine accessibility, while health
status affects method suitability.

49. Evaluate the role of reproductive technologies in addressing global food security:

Model Answer: Reproductive technologies contribute to food security through development of

high-yielding crop varieties, disease-resistant plants, and improved livestock breeds. Tissue
culture enables rapid multiplication of superior varieties. Genetic engineering creates crops
with enhanced nutritional content and stress tolerance. Animal reproductive technologies
improve breeding efficiency and genetic gain. However, concerns about genetic diversity loss,
farmer dependency on technology, and equitable access must be addressed for sustainable
food security.

50. Discuss the evolutionary implications of organisms that can switch between sexual and
asexual reproduction:

Model Answer: Organisms with facultative reproductive strategies have evolutionary

advantages through temporal and spatial flexibility. They can reproduce asexually during
favorable conditions for rapid population growth, then switch to sexual reproduction during
environmental stress to generate adaptive diversity. This strategy allows exploitation of
multiple ecological niches and provides insurance against environmental unpredictability.
Examples include aphids, Daphnia, and many plants that demonstrate the evolutionary
success of reproductive flexibility.

Summary and Key Points {#summary}

Essential Concepts for Examination Success

Asexual Reproduction Mastery Points: Understanding asexual reproduction requires

recognizing that it involves a single parent producing genetically identical offspring without
gamete formation. The key types you must distinguish are binary fission in unicellular
organisms like Paramecium, budding in organisms like yeast, and various forms of vegetative
propagation in plants. For examination success, remember that natural vegetative propagation
includes runners, rhizomes, bulbs, and tubers, while artificial methods encompass grafting,
budding, and cutting techniques that humans use in agriculture.

Sexual Reproduction in Plants - Critical Understanding: Sexual reproduction in flowering

plants centers on the flower structure and the remarkable process of double fertilization that
distinguishes angiosperms. You must understand that stamens produce pollen containing
male gametes, while pistils contain ovules with female gametes. The process involves
pollination (transfer of pollen), followed by double fertilization where one sperm fertilizes the
egg to form the embryo, and another fertilizes polar nuclei to form the endosperm. This
understanding connects to fruit and seed development, which are frequently tested topics.

Mammalian Reproduction Complexity: Mammalian reproduction involves intricate hormonal

regulation, complex anatomical structures, and precise developmental timing. The male
reproductive system focuses on continuous sperm production through spermatogenesis,
while the female system operates cyclically through the menstrual cycle. Understanding the
hormonal interplay between hypothalamus, pituitary, and gonads is crucial for explaining
reproductive processes and their regulation.
Strategic Study Approaches

Comparative Analysis Method: Successful students develop strong comparative thinking

skills. Practice creating comparison tables between asexual and sexual reproduction, different
pollination methods, male and female reproductive systems, and various contraceptive
methods. This approach helps you quickly identify correct answers in multiple-choice
questions and structure comprehensive essay responses.

Process Understanding Over Memorization: Rather than memorizing isolated facts, focus on
understanding processes and their biological significance. For example, understand why
cross-pollination is advantageous (genetic diversity), how hormonal feedback loops maintain
reproductive cycles, and why certain agricultural practices work (grafting compatibility, tissue
culture conditions). This deeper understanding helps you tackle unfamiliar question formats.

Application to Real-World Scenarios: Connect reproductive concepts to practical applications

in agriculture, medicine, and biotechnology. Understanding how farmers use vegetative
propagation, how doctors apply reproductive knowledge in fertility treatments, and how
biotechnologists use tissue culture for crop improvement demonstrates the practical
relevance of theoretical knowledge.

Examination Strategies

Question Pattern Recognition: JAMB and WAEC questions often follow predictable patterns.
Asexual reproduction questions frequently ask about identifying methods, advantages and
disadvantages, or agricultural applications. Sexual reproduction questions commonly focus
on flower structure, pollination agents, fertilization processes, or hormonal regulation.
Recognizing these patterns helps you anticipate question types and prepare accordingly.

Common Mistake Avoidance: Many students confuse binary fission with budding, or mistake
natural for artificial vegetative propagation. Others mix up male and female reproductive
structures or misunderstand hormonal timing in reproductive cycles. Identifying these
common misconceptions and explicitly learning the correct distinctions significantly improves
examination performance.

Time Management in Examinations: Reproduction questions often appear as both multiple-

choice and essay questions. For multiple-choice questions, quickly eliminate obviously
incorrect options and focus on distinguishing between remaining choices. For essay
questions, structure your response using the process understanding approach, beginning with
definitions, explaining processes step-by-step, and concluding with significance or
applications.

Advanced Understanding for ABU Post-UTME

Molecular and Cellular Perspectives: ABU Post-UTME may include more sophisticated
questions requiring understanding of cellular processes underlying reproduction. This includes
knowledge of meiosis in gamete formation, mitosis in development, and molecular
mechanisms of fertilization. Understanding these cellular foundations provides the depth
needed for advanced questions.

Biotechnology Applications: Advanced reproductive technologies like IVF, genetic engineering,

and tissue culture represent cutting-edge applications of reproductive biology. Understanding
the principles underlying these technologies, their benefits and limitations, and their role in
addressing human needs demonstrates the advanced thinking that distinguishes top
performers.

Evolutionary and Ecological Context: Superior students understand reproduction within

broader biological contexts. This includes recognizing how reproductive strategies relate to
evolutionary success, how environmental factors influence reproductive choices, and how
human activities affect reproductive processes in both crops and natural populations.

Final Preparation Recommendations

Active Recall Practice: Test yourself regularly without looking at notes. Practice explaining
reproductive processes aloud, drawing diagrams from memory, and solving problems without
references. This active recall strengthens memory and identifies knowledge gaps that need
attention.

Integration Across Topics: Reproduction connects to genetics, evolution, ecology, and applied
biology. Practice making these connections explicit. Understanding how reproductive
processes influence genetic inheritance, evolutionary adaptation, and ecological relationships
demonstrates comprehensive biological understanding.

Current Applications Awareness: Stay informed about current developments in reproductive

biology, agricultural biotechnology, and medical applications. Understanding contemporary
issues like genetic modification in crops, fertility treatments, and conservation biology
applications shows engagement with the living science behind the examination content.

Remember that reproduction is fundamentally about the continuation of life, and this central
biological importance explains why it appears prominently in examinations. Your thorough
understanding of reproductive processes positions you not only for examination success but
also for appreciating the remarkable diversity of life strategies that surround us.

The depth and breadth of knowledge in these notes provide you with the comprehensive
foundation needed for exceptional performance in your JAMB, WAEC, and ABU Post-UTME
examinations. Approach your studies systematically, practice regularly, and maintain
confidence in your preparation as you work toward achieving your academic goals. The corpus
luteum forms from the remnants of the Graafian follicle after ovulation.*

11. Which type of placentation is found in legumes? A) Axile B) Parietal C) Marginal D)

Central

Answer: C Explanation: Legumes (pea family) have marginal placentation where ovules are
attached to the ovary margin.

12. The hormone responsible for milk production is: A) Prolactin B) Oxytocin C) Estrogen D)
Progesterone

Answer: A *Explanation: