Grade 9 Biology – Core Vocabulary

A set of core vocabulary flashcards summarising key terms from Grade 9 Biology units on Circulatory System, Reproduction, Biodiversity, and Photosynthesis.

Blood Circulatory System

The transport system in humans consisting of the heart, blood and blood vessels.

Heart

A muscular pumping organ that propels blood through the vessels.

Blood

A fluid tissue composed of plasma, red blood cells, white blood cells and platelets.

Plasma

Pale yellow liquid part of blood that transports water, nutrients, wastes and gases.

Red Blood Cell (RBC)

Biconcave, nucleus-less blood cell containing haemoglobin for oxygen transport.

Haemoglobin

Red pigment in RBCs that binds oxygen to form oxy-haemoglobin.

White Blood Cell (WBC)

Blood cell that defends the body by engulfing germs or producing antibodies.

Platelet

Cell fragment that helps blood clot to prevent bleeding and infection.

Artery

Blood vessel with thick, elastic walls carrying blood away from the heart under high pressure.

Vein

Blood vessel with a large lumen and valves that carries blood toward the heart under low pressure.

Capillary

Microscopic vessel with one-cell-thick wall where exchange of substances occurs between blood and tissues.

Pulse

Rhythmic stretching of artery walls following each heartbeat, felt at wrist or neck.

Cardiovascular Disease (CVD)

Non-communicable disorder affecting heart or blood vessels, e.g. heart attack, stroke.

Heart Attack

Damage to heart muscle when its blood supply is blocked, often by fatty deposits.

Stroke

Loss of brain function due to interrupted blood flow to the brain.

Hypertension

Persistently high blood pressure that can damage vessel walls.

Valve (in veins)

Flap-like structure preventing backflow of blood in veins.

Blood Clotting

Series of reactions, involving platelets, forming a clot to stop bleeding.

Reproduction

Biological process that produces new individuals of the same species.

Asexual Reproduction

Mode of reproduction involving one parent and producing genetically identical offspring.

Sexual Reproduction

Mode of reproduction involving two parents and fusion of male and female gametes.

Gamete

Specialised sex cell (sperm or ovum) that fuses during fertilisation.

Sperm

Motile male gamete produced in testes.

Ovum (Egg)

Large non-motile female gamete produced in ovaries.

Zygote

Fertilised egg cell formed after fusion of sperm and ovum.

Fertilisation

Fusion of male and female gametes to form a zygote.

Testis

Male organ that produces sperm and the hormone testosterone.

Ovary

Female organ that produces ova and hormones oestrogen and progesterone.

Oviduct (Fallopian Tube)

Tube that carries ovum from ovary to uterus; usual site of fertilisation.

Uterus

Muscular organ where embryo implants and foetus develops.

Cervix

Narrow neck of uterus opening into the vagina.

Vagina

Muscular canal receiving sperm and acting as birth canal.

Penis

External male organ that delivers semen into female vagina.

Sperm Duct (Vas Deferens)

Tube transporting sperm from testis to urethra.

Urethra (male)

Duct conducting urine or semen to outside of body.

Seminal Vesicle

Gland adding nutrient-rich fluid to semen.

Prostate Gland

Gland secreting alkaline fluid that makes up part of semen.

Scrotum

Sac that holds testes outside the body for optimal temperature.

Embryo

Early developmental stage after zygote division and before foetus formation.

Foetus

Developing human baby from about eight weeks after fertilisation until birth.

Sexually Transmitted Disease (STD)

Infection spread primarily by sexual contact, e.g. HIV/AIDS, syphilis.

HIV/AIDS

Viral STD where Human Immunodeficiency Virus attacks immune cells causing Acquired Immune Deficiency Syndrome.

Syphilis

Bacterial STD caused by Treponema pallidum, producing sores and systemic damage if untreated.

Gonorrhea

Bacterial STD affecting mucous membranes, caused by Neisseria gonorrhoeae.

Opportunistic Disease

Illness that exploits weakened immunity, common in AIDS patients.

Biodiversity

Variety and abundance of different species in a defined area.

Species

Group of organisms that can interbreed to produce fertile offspring.

Ecosystem

Community of living organisms interacting with their physical environment.

Quadrat

Square frame used to sample and estimate numbers of organisms in a habitat.

Deforestation

Large-scale removal of forests leading to habitat loss and reduced biodiversity.

Pollution

Introduction of harmful substances into environment affecting organisms and ecosystems.

Overexploitation

Unsustainable harvesting of natural resources leading to population decline.

Invasive Alien Species

Non-native organisms that out-compete native species and disrupt ecosystems.

Habitat Loss

Destruction or alteration of natural environment causing decline of species.

Natural Calamity

Natural event such as cyclone, drought or flood that can reduce biodiversity.

Endemic Species

Species native to and restricted within a particular geographic area.

Ecotourism

Environmentally responsible travel to natural areas that conserves biodiversity and benefits locals.

Photosynthesis

Process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen.

Chlorophyll

Green pigment in chloroplasts that captures light energy for photosynthesis.

Chloroplast

Organelle in plant cells where photosynthesis occurs.

Stomata (singular: Stoma)

Pores in leaf epidermis that regulate gas exchange and transpiration.

Xylem

Vascular tissue transporting water and minerals from roots to leaves.

Phloem

Vascular tissue transporting sugars from leaves to the rest of the plant.

Glucose

Simple sugar produced during photosynthesis; primary energy source for cells.

Starch

Insoluble carbohydrate formed by linking glucose molecules for storage in plants.

Variegated Leaf

Leaf with green and non-green patches, used to investigate chlorophyll’s role in photosynthesis.

Palisade Mesophyll

Layer of elongated, chloroplast-rich cells beneath upper epidermis where most photosynthesis occurs.

Spongy Mesophyll

Loosely arranged leaf tissue with air spaces aiding gas diffusion.

Midrib

Central vein of a leaf supporting structure and housing vascular bundles.

Vein (leaf)

Vascular bundle of xylem and phloem distributing water and food within a leaf.

Word Equation for Photosynthesis

Carbon dioxide + Water (light, chlorophyll) → Glucose + Oxygen

Light Energy

Solar energy absorbed by chlorophyll to drive photosynthesis.

Oxy-haemoglobin

Compound formed when haemoglobin binds oxygen for transport.