A community of lifelong learners, responsible global citizens and champions of success
Cells and cell specialisation Cells are the basic building blocks of any living organism. They carry out all the processes necessary for the survival of the organism. Plants and animals are made up of thousands or millions of microscopic cells. Cells contain cytoplasm enclosed in a cell membrane. Many chemical reactions take place in the…
Read More “Cells and cell specialisation (Combined Science)” »
Photosynthesis Photosynthesis is the manufacture of carbohydrates by a green plant using carbon dioxide, water and light energy in the presences of chlorophyll. According to the definition above: the raw materials of photosynthesis are carbon dioxide and water. light is the source of the energy required for photosynthesis to take place. chlorophyll is required as…
Leaf structure A leaf is attached to the stem by a leaf stalk, which continues into the leaf as a midrib supporting the whole leaf structure. A network of veins branches from the midrib delivering water and salts to the leaf cells and also carrying away the food made by the leaves. Epidermis The epidermis…
Human nutrition Just like all living organisms, humans need food to survive. One important difference between plant nutrition and human nutrition (animal nutrition) is that green plants can manufacture their own food by photosynthesis but animals have can’t manufacture their own food. They have to eat food made by plants. Both plants and animals use…
Malnutrition Malnutrition refers to either getting too much food or too little food or the wrong type of food. If a person’s total food intake is not enough to meet the body’s energy demands, the body breaks down its own tissues to provide the energy to stay alive. This causes loss of weight, muscle wastage,…
Digestion Digestion is the breakdown of complex insoluble food particles into smaller soluble molecules that can be easily absorbed by the body. Digestion occurs in the alimentary canal. Alimentary canal The alimentary canal is a long digestive tube running through the body from the mouth to the anus. The alimentary canal has many functions besides…
Structure of teeth The structure of teeth of an animal correlates to its diet. Humans are called omnivores because they eat both animal and plant material. Humans have incisors, canines, premolars and molars, each type of teeth determined in size and shape by its function: The incisors cut pieces off the food, such as when…
Respiratory System The human respiratory system is responsible for taking oxygen into the respiring cells and carbon dioxide out of the respiring cells. All the body processes, for example movement, growth and reproduction, require energy. Unlike plants which can obtain energy directly from the sun, animals (humans included) obtain energy only from the food they…
Respiration Respiration involves the breakdown of carbohydrates in living organisms to release energy. The respiration we are going to talk about here is a chemical process that occurs in cells and involves the use of enzymes, not the process of breathing, which is sometimes also called respiration. A lot of the processes that takes place…
Transport in plants Leaf The leaf has a midrib which contains xylem and phloem vessels for the transport of water to the leaves and food from the leaves respectively. Stem The stem: carries food from the leaves to all parts of the plant carries water and dissolved salts from the roots to the leaves. supports…
Diffusion, osmosis and active uptake (Combined Science) Diffusion Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration. Diffusion occurs along the concentration gradient. A concentration gradient is the difference in concentration between a region of higher concentration of a substance and a region of lower…
Circulatory System The mammal circulatory system consists of the heart, blood and the blood vessels. There are different types of blood vessels, each type with its own functions, for example, arteries carry blood from the heart to the rest of the body and veins return blood from the body organs back to the heart. Arteries…
Sexual reproduction in plants Flowers contain the reproductive organs for sexual reproduction in plants. The stamens are the male organs which produce pollen and the carpels are the female organs which receive the pollen grains. After fertilisation, it is the carpel becomes the fruit and contains the seeds. Stamens Stamens are the male reproductive organs…
Reproduction in humans Reproduction is the process in which parent species produce new individuals (offspring). In human reproduction the two sexes, the male species produce the male sex cells (sperm or spermatozoa) and the female species produce the female sex cells (ova, singular = ovum) Male Reproductive System Sperm are produced in the male reproductive…
Ecosystems An ecosystem (short for ecological system) is a self-contained system of interdependent organisms and their natural environment. Every ecosystem is driven by light energy from the sun which enters the system via the green plants and is then passed on to the animals as chemical energy when they eat the plants. For example, in…
Carbon cycle in the ecosystem The carbon cycle is a cycle by which carbon is exchanged between the ecosystem and atmosphere of the Earth. Carbon is the main component of all living organisms and the carbon cycle comprises a sequence of events that make the Earth capable of sustaining life. The carbon cycle Related ContentO…
Malaria Malaria is a disease caused by a protozoan parasite called Plasmodium. Plasmodium is the pathogen that causes malaria. A pathogen is disease causing organism.Related ContentEcosystemsCombined Science Questions (Page 2)ProjectilesDelta Variant Pushes Herd Immunity Threshold Above 80%KinematicsVectors Part 1 (O level Maths)Delta Variant Makes Herd Immunity Impossible – AstraZeneca ScientistStructure of teeth Malaria is spread…