Grade 8 Biology: Responding to the Environment and Body Systems

Comprehensive vocabulary flashcards covering tropisms, the anatomy and disorders of the eye, ear, and skin, the nervous system, cellular respiration, and the menstrual cycle.

Stimulus

Any change in an organism's environment that causes the organism to react.

Response

How an organism reacts to a stimulus.

Tropism

Plant growth in response to a stimulus; derived from the word "tropo" meaning "turn."

Phototropism

Plant growth in response to light.

Geotropism

Plant growth in response to gravity.

Thigmotropism

Plant growth in response to touch.

Hydrotropism

Plant growth in response to water.

Chemotropism

Plant growth in response to chemical stimuli.

Thermotropism

Plant growth in response to heat.

Positive Tropism

Growth towards a stimulus.

Negative Tropism

Growth away from a stimulus.

Sclerotic layer

A tough, white-coloured protective layer that surrounds the eye and helps maintain its shape.

Conjunctiva

A clear, thin layer covering the front of the eye.

Cornea

A clear 'window' in the sclerotic layer and under the conjunctiva that allows light to enter the eye.

Pupil

A hole in the centre of the iris that dilates in the dark to let more light in.

Vitreous humour

A jelly that helps maintain the shape of the eye.

Choroid

A black layer behind the lens that prevents light from reflecting all around the eye and nourishes it with blood and oxygen.

Retina

A layer containing over $100$ million light-sensitive cells which transmit messages to the brain.

Yellow spot (fovea)

A section of the retina directly behind the pupil that contains a large number of colour-sensitive cells for clear vision.

Blind spot

The area where blood vessels and the optic nerve join the eyeball; it lacks light-sensitive cells.

Aqueous humour

A watery liquid that fills the space between the cornea and the lens to help maintain the shape of the eye.

Iris

The part of the eye that changes size to control the pupil size and gives eyes their colour.

Optic nerve

The structure that joins the eye to the brain and passes information about the image for processing.

Lens

A clear jelly-like 'window' that helps focus an image on the back surface of the eye.

Suspensory ligaments

The structures that hold the lens in place.

Ciliary muscles

Muscles that change the shape of the lens to bring images into focus.

Myopia

Near-sightedness caused by an eyeball being "too long," making distance vision blurry.

Hyperopia

Far-sightedness caused by an eyeball being "too short," making near objects blurry.

Astigmatism

A condition occurring when the cornea is irregularly shaped (football-shaped), causing a smudged appearance for near and far objects.

Presbyopia

Age-related inability to focus on objects up close due to the lens losing elasticity.

Glaucoma

An eye disorder resulting from high pressure (Ocular Hypertension) that damages the optic nerve.

Cataracts

A condition where proteins clump in the lens to create a cloudy area that distorts light and damages vision.

Tinnitus

A roaring in the ears.

Meniere’s disease

A condition that may be the result of fluid problems in the inner ear affecting hearing or balance.

Ear barotrauma

An injury to the ear resulting from changes in barometric (air) or water pressure.

Liver spot

Flat brown or black spots that appear on skin exposed to sunlight.

Scabies

An itchy skin condition caused by the tiny burrowing mite Sarcoptic scabies.

Athlete’s Foot (Tinea pedis)

A fungal infection that usually begins between the toes.

Acne

A common skin condition where pores clog, forming spots or pimples.

Epidermis

The topmost layer that protects the skin from infection.

Hair erector muscle

Muscles that contract to trap air for insulation and relax to reduce insulation.

Hypodermis

The layer of skin responsible for insulation and contributing to vitamin D production.

Sebaceous gland

A gland that secretes an oily substance to coat hairs.

Dermis

The skin layer where blood vessels and nerves are located.

Malpighian layer

The layer containing melanin that protects the skin against ultraviolet rays.

Keratin

A protein in the skin that helps form a protective, waterproof outer layer.

Central nervous system

The part of the nervous system made up of the brain and spinal cord.

Peripheral nervous system

Nerves that branch off from the spinal cord and extend to all parts of the body.

Cerebral palsy

A group of conditions affecting movement and posture caused by brain damage, often from lack of oxygen before birth.

Epilepsy

A brain disease where nerve cells do not signal properly, causing seizures.

Cellular respiration

The process by which cells in plants and animals break down sugar and turn it into energy.

Aerobic Respiration

Respiration occurring in the presence of oxygen where glucose is completely broken down ($glucose + oxygen \rightarrow carbon\,dioxide + water + energy$).

Anaerobic Respiration

Respiration in the absence of oxygen; in yeast, it produces ethanol ($glucose \rightarrow ethanol + carbon\,dioxide + energy$).

Alveoli

Small bags at the end of bronchioles where gas exchange takes place.

Haemoglobin

The substance in red blood cells that combines with oxygen to make oxyhaemoglobin.

Menstruation

The loss of the uterine lining at the start of the cycle if no fertilisation has occurred.

Ovulation

The release of an egg occurring around day $14$ of the menstrual cycle.

Oestrogen

A hormone that peaks before day $14$, causing the uterine wall to thicken and the egg to mature.

Progesterone

A hormone that rises after ovulation to further thicken the uterine lining; a fall in its level causes menstruation.