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Unit notes and practice questions

Grade 9 Biology unit 4: Reproduction

Everything here is for unit 4 of the Grade 9 Biology textbook: what the chapter covers, the short notes, practice questions with their answers, and the lesson video where one exists.

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4
Cards
10
Practice questions on unit 4
74–102
The textbook pages for unit 4

Short notes for unit 4

The cards filed under this chapter on the Grade 9 Biology page. Open one at a time.

STI NameCausative PathogenPathogen TypeCurable with Antibiotics
TrichomoniasisTrichomonas vaginalisProtozoanNo (uses antiprotozoal drugs)
ChlamydiaChlamydia trachomatisBacteriumYes
GonorrheaNeisseria gonorrhoeaeBacteriumYes
SyphilisTreponema pallidumBacteriumYes
HIV/AIDSHuman Immunodeficiency VirusVirusNo (managed with antiretroviral drugs)

When you use it

Use when identifying causative agents, pathogen classes, and treatment mechanisms of STIs.

Watch out

Antibiotics cure bacterial STIs like syphilis and gonorrhea, but they have no effect on viral infections like HIV.

Drafted from Grade 9 Biology, pages 74-102, then checked twice before it went up

When you use it

Use when evaluating the function, effectiveness, and limitations of different family planning methods.

Watch out

Hormonal pills, injections, implants, IUDs, diaphragms, and surgical sterilizations prevent pregnancy but provide zero protection against STIs. Only abstinence and latex condoms protect against both.

Drafted from Grade 9 Biology, pages 74-102, then checked twice before it went up

HormoneSecreted ByPrimary Function in Menstrual Cycle
FSHPituitary glandStimulates follicle growth and estrogen secretion
EstrogenOvarian follicleThickens uterine endometrium and triggers LH surge
LHPituitary glandTriggers ovulation and converts ruptured follicle to corpus luteum
ProgesteroneCorpus luteumMaintains thickened uterine lining for embryo implantation

When you use it

Use when tracing the roles and sequence of pituitary and ovarian hormones during the female reproductive cycle.

Watch out

Ovulation is directly triggered by the surge in LH, not by FSH or progesterone.

Drafted from Grade 9 Biology, pages 74-102, then checked twice before it went up

ModeKey MechanismOrganism Examples
Binary/Multiple FissionParent divides into two or more equal daughter cellsBacteria, Malarial parasites
FragmentationParent breaks into pieces that regenerate into complete bodiesSpirogyra, Worms
BuddingParent divides unequally by forming an outgrowth or budYeast, Hydra
Vegetative PropagationNew plant grows from vegetative parts like runners, rhizomes, tubersStrawberry, Couch grass, Potato
ParthenogenesisUnfertilized egg develops directly into an adult organismHoneybee drones, Whiptail lizard

When you use it

Use when identifying or comparing the different mechanisms of asexual reproduction in organisms.

Watch out

Budding produces unequal daughter units, whereas binary fission divides the parent into approximately equal parts.

Drafted from Grade 9 Biology, pages 74-102, then checked twice before it went up

Practice questions on unit 4

10 multiple-choice questions written against this chapter, each with its answer and the reason. Try one before you open the answer.

Question 1

What is the term for the type of asexual reproduction in which an unfertilized egg develops into an adult organism, such as a male drone honeybee?

  1. A.Binary fission
  2. B.Parthenogenesis
  3. C.Fragmentation
  4. D.Budding
Show the answer and why

Answer: B Parthenogenesis

Why

Parthenogenesis is a form of asexual reproduction where an unfertilized egg develops directly into an adult organism without being fertilized by sperm.

Question 2

Which part of a human sperm cell contains many mitochondria that supply energy for swimming?

  1. A.Head
  2. B.Acrosome
  3. C.Midsection
  4. D.Tip of the tail
Show the answer and why

Answer: C Midsection

Why

The midsection of the sperm contains numerous mitochondria that produce the energy required for the flagellum to move.

Question 3

At what stage of development is a human embryo called a fetus?

  1. A.After 2 weeks
  2. B.After 4 weeks
  3. C.After 8 weeks
  4. D.After 20 weeks
Show the answer and why

Answer: C After 8 weeks

Why

After 8 weeks of development, when all the organs are formed, the embryo is referred to as a fetus.

Question 4

Which sexually transmitted infection is caused by the flagellated protozoan Trichomonas vaginalis?

  1. A.Syphilis
  2. B.Gonorrhea
  3. C.Chlamydia
  4. D.Trichomoniasis
Show the answer and why

Answer: D Trichomoniasis

Why

Trichomoniasis is caused by the flagellated protozoan parasite named Trichomonas vaginalis.

Question 5

Underground horizontal stems that arise from lateral buds and grow beneath the soil, such as in couch grass, are called:

  1. A.Stolons
  2. B.Rhizomes
  3. C.Bulbs
  4. D.Corms
Show the answer and why

Answer: B Rhizomes

Why

Rhizomes are horizontal stems that grow underground and produce buds at their nodes that can develop into shoots above the ground.

Question 6

During the human menstrual cycle, which hormone surges from the pituitary gland to trigger ovulation?

  1. A.Luteinizing hormone (LH)
  2. B.Progesterone
  3. C.Testosterone
  4. D.Thyroxine
Show the answer and why

Answer: A Luteinizing hormone (LH)

Why

A high level of estrogen causes the pituitary gland to release a surge of luteinizing hormone (LH), which causes the follicle to swell, burst, and release an egg (ovulation).

Question 7

A health worker in Hawassa is explaining birth control methods. Which method involves inserting a small 4 cm plastic tube under the skin of the upper arm to release progesterone for about 3 years?

  1. A.Contraceptive injection
  2. B.Contraceptive implant
  3. C.Intra-uterine device (IUD)
  4. D.Diaphragm
Show the answer and why

Answer: B Contraceptive implant

Why

The contraceptive implant is a small plastic tube inserted under the skin of the upper arm that slowly releases progesterone and lasts for about 3 years.

Question 8

Why are the human testes located permanently outside the abdominal cavity in the scrotum?

  1. A.To protect developing sperm from urinary acid
  2. B.To increase blood flow to the prostate gland
  3. C.To maintain a slightly lower temperature needed for viable sperm formation
  4. D.To make it easier for sperm to travel through the ureter
Show the answer and why

Answer: C To maintain a slightly lower temperature needed for viable sperm formation

Why

The scrotum provides an environment with a slightly lower temperature than the rest of the body, which is required for viable sperm to develop properly.

Question 9

According to the textbook, what percentage of identical (monozygotic) human twins have separate placentas?

  1. A.About 10%
  2. B.About 33%
  3. C.About 50%
  4. D.About 67%
Show the answer and why

Answer: B About 33%

Why

About 33% of identical twins develop with separate placentas, while the remaining identical twins share a single common placenta.

Question 10

Which sexually transmitted infection is caused by the spiral shaped bacterium Treponema pallidum and can cause skin chancres, followed by damage to the bones, liver, and brain if left untreated?

  1. A.Syphilis
  2. B.Gonorrhea
  3. C.Chlamydia
  4. D.Trichomoniasis
Show the answer and why

Answer: A Syphilis

Why

Syphilis is caused by the spiral shaped bacterium Treponema pallidum. It produces chancres and can damage internal organs including the brain if not treated with antibiotics.

The app holds 12 questions on this unit, marked as you go. These are the first 10.

The textbook pages for unit 4

Unit 4 runs from page 74 to page 102 of the Ministry of Education edition.

Ministry of Education edition, English, 165 pages

Download the PDF

All Grade 9 Biology short notes

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