Science

Biology

Trophic cascade

The levels of predators and preys in an ecosystem.

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Preditor and prey relationship

An interaction between two organisms of unlike species in which one of them acts as predator that feeds on the other organism that is the prey.

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Competition between species

In ecosystems, organisms compete for the resources they need to survive, grow, and reproduce. Animals compete for air, food, shelter, water, and space. Plants also compete with each other for the resources they need, including air, water, sunlight, and space.

Symbiosis

When different species live side by side, interacting with each other over long periods of time.

Three types of symbiotic relationships

Mutulaism, parasitism, commensalism

Mutualism

Is when both species benefit from the relationship.

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Parasitism

Is when one species benefits and the other species is harmed.

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Commensalism

Is when one species benefits and the other species isn’t affected.

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Example of mutualism

Oxpecker (bird) feeds on the ticks that live on the surface of the buffalo’s skin. They feed off these ticks as a food source, so then the ticks don’t enter the bloodstream of the buffalo and harm them.

Example of parasitism

Fleas harm their hosts, such as dogs, by biting their skin, sucking their blood, and causing them to itch. The fleas, in turn, get food and warm shelter.

Example of commensalism

A bird making a nest in a tree. The tree provides shelter and protection to the bird without getting harmed or affected by the bird.

Three levels of biodiversity

1. Genetic diversity
2. Species diversity
3. Ecosystem diversity

Axon

The part of a neuron that carries impulses to other neurons

Chemoreceptors

Are sensitive to chemicals, such as odour molecules in the air, and are located in the nose and tongue.

Mechanoreceptor

Are sensitive to touch, pressure, sound as well as motion. They are located in the skin, the inner ear and muscles.

Pain receptors

Are sensitive to chemical changes in damaged cells and are located throughout the body, but most are located in the skin.

Thermoreceptors

Are sensitive to temperature changes and are located in the skin.

Photoreceptors

Are sensitive too light and are located in the eyes.

Dendrite

Is where a neuron receives input from other cells.

Olfactory epithelium

Is tissue in the nose that contains receptor cells for smell. They are also a type of chemoreceptor.

Retina

Is tissue in the eye that contains receptor cells for light.

Synapse

The gap between neurons where signals are sent from one to the other.

Explain why all endocrine glands have blood vessels coming from them

Instead of using nerves to transmit information, the endocrine system uses blood vessels to deliver hormones to cells.

Adrenal gland

A gland above the kidney that prepares the body for an emergency.

Circulatory system

The endocrine system relies on the circulatory system to deliver hormones where they are needed.

Endocrine gland

An organ that releases hormones to be used inside the body

Humans have endocrine glands in different areas of the body, including the brain, throat and gonads.

General effect

The action of a hormone on all cells in the body for example, adrenaline affects the whole body by increasing heart rate, releasing energy to muscles and slowing digestion.

Cellular respiration

The reaction in living cells that releases energy for life processes. Cellular respiration converts sugar and oxygen into water and carbon dioxide, releasing usable energy.

Specific effect

The action of a hormone on only some cells in the body.

Target cell

A cell that can be affected by a certain hormone

Negative feedback loop

Is a change in a system that reduces the effect.

Positive feedback loop

Is a change in a system that amplifies the effect.

What is the nervous system

The body system that senses the environment and controls actions. It is made up of two main divisions, the central nervous system and the peripheral nervous system.

Describe the central nervous system

The central nervous system consists of the brain and spinal cord. It is sometimes called the “co-ordinator” because it makes sense of the messages it receives from the sense organs and co-ordinates responses by the muscles and glands.

Describe the peripheral nervous system

The peripheral nervous system consists of all the nerves extending from the brain and spinal cord. The bundle of nerves then relay messages between the sense organs, the central nervous system, the muscles and glands. This system is spread out through the entire body.

Describe the difference between a food chain and food web

Food chains show a single path of energy flow through organisms in an ecosystem. While a food web shows all the different paths of energy flow through organisms in an ecosystem.

Outline what a food chain represents

A food chain diagram includes a series of arrows, each pointing from one species to another, representing the flow of energy from one feeding group of organisms to another.

Identify how energy enters food webs

Energy enters the food web because plants and other producers get their energy from sunlight through the process of photosynthesis.

Explain why energy is lost in each step of the food chain

Not all the energy is passed from one level of the food chain to the next. About 90 per cent of energy is either released during cellular respiration, or lost through movement, heat or in the materials that the consumer does not digest.

Explain how energy is transferred through food webs

Energy is transferred through the metabolism of organisms consuming other organisms.

Describe the two essential processes that allow energy to enter and leave the food web

Energy enters the food web through the process of photosynthesis. Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar. Energy leaves the food web through cellular respiration. Cellular respiration is the process that occurs in the mitochondria of organisms to break down sugar in the presence of oxygen to release energy in the form of ATP.

Outline what biodiversity is

Biodiversity is the variety of living things in an area.

Explain the importance of biodiversity

Biodiversity is very important because if an ecosystem experiences a threatening event, the ecosystem that consists of high biodiversity will be able to recover after the change, this is called resilience.

Identify two areas that humans have affected ecosystems and explain how it has impacted biodiversity

Humans have affected ecosystems through deforestation and overfishing. Deforestation can directly lead to biodiversity loss when animal species that live in the trees no longer have their habitat, cannot relocate, and therefore become extinct. Overfishing occurs when fish are removed from an ecosystem faster than they can reproduce, this then creates an imbalance that can erode the food web and lead to a loss of other important marine life.

Describe how biodiversity can help humans

Biodiversity helps humans because it contains food, shelter, fuel and medicine.

What is the carbon cycle

The carbon cycle is the process in which carbon atoms continually travel from the atmosphere to the Earth and then back into the atmosphere.

Explain the importance of the carbon carbon cycle

It is important because the carbon compounds regulate the Earth's temperature, makes up the food that sustains organisms, and provides energy that fuels the global economy.

Carbon cycles through ecosystems through respiration, decomposition and excretion and carbon, being released into the soil and atmosphere then continuing the cycle.

Describe how humans have altered the carbon cycle

Humans affect the carbon cycle by burning fossil fuels and cutting down trees.

Identify the sensory organs that allow us to interact with our environment

The sensory organs are ear, tongue, eyes, nose and skin.

Identify the main parts of a neuron

The main parts of a neuron are the cell body where the nucleus is located, dendrites which are branches that receive messages, an axon which is a thread like structure that carries impulses to their neurons and a myelin sheath which is a fatty layer that insulates the axon as well as sometimes a dendrite.

Identify the three types of neurons

1. Sensory neurons transmits messages from sensory organs to the central nervous system.
2. Interneurons transmit messages from sensory neurons to motor neurons.
3. Motor neurons transmit messages from the central nervous system to ”effectors” such as muscles and glands to initiate a response.

Describe what a stimulus-response pathway is, give an example.

A stimulus-response pathway is the series of events in the nervous system that lead to a response.


1. A receptor detects the stimulus. For example, thermoreceptors in the skin detect heat from a candle.
2. A sensory neuron transmits the signal to a co-ordinator in the spinal cord or brain.
3. A motor neuron transmits a signal to an effector -muscle or gland- which produces a response. For example muscle in the arm pull the hand away from the hot candle.

Outline what the endocrine system is

The body system that produces hormones to control body functions.

Outline what a hormone is

A chemical messenger that controls a particular body function.

Identify three different hormones and explain what their function is

Adrenaline - A hormone that prepares the body to respond to an emergency as well as having general effects, such as increasing heart rate, stopping digestion and releasing energy to muscles.

Thyroxine - increases the rate of chemical reactions in cells and helps control growth and development.

Insulin - A hormone that helps to lower blood glucose.

Outline what a gland is

An organ that releases chemical substances to assist the body.

Identify three glands and their functions

Thyroid gland - A gland in the neck that controls growth and normal body function

Pituitary gland - A gland in the brain that regulates daily rhythms like sleep

Pancreas - A gland behind the stomach that helps digestion and blood glucose control

Outline what homeostasis is and explain its importance

Homeostasis is the body’s ability to maintain a stable state. The effect of changes in salt and water levels, as well as the temperature of the body, are all under the control of homeostasis, which keeps the body stable. Without homeostasis, the enzymes and other biological systems that make life possible will not work as they should.

Describe two examples of how homeostasis works in the body

Two examples of homeostasis is body temperature regulation, blood pressure regulation and blood sugar regulation.

Explain how the nervous system and endocrine system work together to maintain a functioning and healthy human body.

The nervous system and the endocrine system work together by coordinating the body's functions to maintain homeostasis during rest and exercise. The nervous and endocrine systems also work together to initiate and control movement, and all the physiological processes movement involves.

Compare and contrast the differences in how the nervous system and endocrine systems work.

The nervous system and endocrine system are both involved in maintaining homeostasis, or stable internal conditions within the body. The primary difference between the two is that the nervous system has acute, rapid effects whereas the endocrine system has longer-lasting, more general effects.

Explain what an outbreak is

An outbreak is a sudden increase in cases of an infectious disease in a particular place.

Example of microbes

bacteria and fungi

What is a pathogen

A pathogen is a microscopic organism or agent that causes disease.

What are three types of pathogens

Bacteria, viruses and fungi.

Are bacteria, viruses and fungi unicellular or multicellular

Bacteria is unicellular, viruses are neither, they are non-living. Fungi is unicellular and multicellular.

Bacteria example

Salmonella, a cause of food poisoning.

Viruses example

Influenza virus, cause of the flu.

Fungi example

Microsporum, cause of athlete’s foot.

Bacteria cells

Small, simple cells without a nucleus

Viruses cells

Viruses don’t have cells instead there is a genetic material in a layer of protein or fat.

Fungi cells

An organism with complex cells that feeds off a living host and they can’t photosynthesis.

Bacteria cause disease by _

Attaching to cells and taking their nutrients; some bacteria produce toxins.

Viruses cause disease by _

Entering cells to reproduce, causing them to burst and die.

Fungi cause disease by _

Feeding off the host; some fungi produce toxins.

Describe the role of the immune system

The immune system is the body system that prevents and fights disease.

Describe how the first line of defence prevents entry of pathogens

The fist line of defence helps stop pathogens from entering the body through physical barriers and kills the pathogens through chemical barriers. The skin acts as a barrier to stop these pathogens from entering the body. Saliva, mucus, tears and urine are important factors in the first line of defence.

Chemical barriers

A defence that kills pathogens before they can enter the body. Stomach acid and the enzymes in saliva and tears are examples of chemical barriers.

Cilia

Microscopic hairs on cells that line the airways. Cilia push out mucus and trapped pathogens from the airways and lungs.

First line of defence

Barriers that prevent pathogens from entering the body. Skin, saliva, urine and tears are barriers in the first line of defence.

Microbe

An organism that is too small to be seen with the naked eye. Microbes include bacteria and some types of fungi.

Mucus

A sticky liquid that lines the nose, throat, lungs and intestines.

Physical barrier

A defence that blocks or traps pathogens before they can enter the body. Skin, mucus and cilia are examples of physical barriers.

Infection

An invasion of the body by pathogens that then multiply.

Inflammation

A painful redness or swelling of part of the body. Inflammation occurs when increased blood flow brings white blood cells to fight invading pathogens.

Phagocytes

A white blood cell that engulfs and destroys pathogens. Phagocytes help fight infections by engulfing and breaking down viruses and bacteria.

Second line of defence

General responses too pathogens inside the body. The second line of defence includes fever, inflammation and phagocytes.

White blood cells

A component of blood that fights infections.

Fever

Fever is an increase in core body temperature above 38°C.
It is usually accompanied by shivering and sweating.
A high temperature slows down or even kills some
pathogens. It also speeds up processes that help the
immune system deal with the threat.

How does puss occur

When dead white blood cells build up at the site of a wound, they form pus.