Biology (KS3)
UK Key Stage 3 biology: cells, body systems, health, photosynthesis, ecology and evolution.
Ämne: Biologi · Nivå: Högstadium (13–15) · 404 kort
Innehåll
- All living organisms are made of cells. Plant and animal cells share many organelles, but plant cells have extras such as a cell wall, chloroplasts and a large permanent vacuole.
- The nucleus contains the cell's genetic material (DNA) and controls the activity of the cell.
- Mitochondria are the site of aerobic respiration, where most of the cell's energy is released from glucose.
- Chloroplasts contain the green pigment chlorophyll and are where photosynthesis takes place in plant cells.
- Ribosomes are tiny organelles where proteins are made inside the cytoplasm.
- Specialised cells include red blood cells (no nucleus, carry oxygen), sperm cells (long tail for swimming), nerve cells (long for carrying signals), root hair cells (large surface area for water uptake) and ciliated cells (tiny hairs to sweep mucus).
- Microscope total magnification is calculated by multiplying the eyepiece lens magnification by the objective lens magnification.
- The levels of organisation in a multicellular body go from cell to tissue to organ to organ system to organism.
- Food travels through the digestive system in the order: mouth, oesophagus, stomach, small intestine, large intestine.
- Digestive enzymes break large food molecules into smaller ones: amylase breaks down starch, protease breaks down proteins, and lipase breaks down fats.
- The small intestine is lined with finger-like villi that give a huge surface area for absorbing digested nutrients into the blood.
- The human heart has four chambers: two atria at the top that receive blood, and two ventricles at the bottom that pump blood out.
- Arteries carry blood away from the heart at high pressure, veins return blood at lower pressure (and have valves), and capillaries are tiny vessels where exchange with tissues happens.
- Blood is made of red blood cells (carry oxygen), white blood cells (fight infection), platelets (help blood clot) and plasma (the liquid that carries everything).
- Haemoglobin is the red protein in red blood cells. It binds oxygen in the lungs and releases it in tissues that need it.
- Air enters the lungs through the trachea, then into bronchi, smaller bronchioles, and finally tiny air sacs called alveoli where gas exchange takes place.
- Breathing means moving air in and out of the lungs. Respiration is the chemical reaction inside cells that releases energy from glucose. They are not the same.
- Aerobic respiration uses oxygen: glucose + oxygen → carbon dioxide + water (+ energy).
- Without enough oxygen, human muscles use anaerobic respiration and produce lactic acid. In yeast, anaerobic respiration (fermentation) produces ethanol and carbon dioxide.
- Photosynthesis takes place in chloroplasts: carbon dioxide + water → glucose + oxygen, using light energy absorbed by chlorophyll.
- Photosynthesis rate is limited by light intensity, carbon dioxide concentration and temperature — these are known as limiting factors.
- Humans have 46 chromosomes arranged in 23 pairs. One chromosome in each pair comes from each biological parent.
- In a food chain, only about 10% of the energy at one level is passed to the next. The rest is lost as heat, movement and waste.
- Charles Darwin proposed natural selection: organisms vary, compete for resources, the best-adapted are more likely to survive and reproduce, and their traits are passed on.
- Evidence for evolution includes fossils in rocks, similar anatomy in related species (e.g. mammal forelimbs), and shared DNA between species.
- Mitosis is the type of cell division that produces two identical daughter cells. Its main stages are prophase, metaphase, anaphase and telophase.
- Stem cells are unspecialised cells that can divide to make new cells of different types. Embryonic stem cells can become any cell, while adult stem cells (such as those in bone marrow) can only become a limited range of cell types.
- Diffusion is the net movement of particles from a higher concentration to a lower concentration. It is how oxygen and carbon dioxide move across the alveoli in the lungs.
- Osmosis is the movement of water across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. It is how water enters plant roots.
- Active transport moves substances against the concentration gradient and uses energy from respiration. Plant roots use active transport to absorb mineral ions like nitrates from the soil.
- Xylem vessels carry water and dissolved mineral ions from the roots up to the leaves. Phloem tubes transport sugars (such as sucrose) made in the leaves to other parts of the plant.
- Transpiration is the loss of water vapour from a plant's leaves, mainly through tiny pores called stomata. It is sped up by high light, high temperature, low humidity and wind.
- Tropisms are plant growth responses to a stimulus. Phototropism is growth towards light; gravitropism (geotropism) is growth in response to gravity — roots grow down, shoots grow up.
- Glucose made in photosynthesis is used for respiration, stored as starch, converted into cellulose to build cell walls, or combined with nitrates from the soil to form proteins.
- After hard exercise the body continues to breathe deeply to repay an oxygen debt: extra oxygen is needed to break down the lactic acid that built up in the muscles.
- Humans have double circulation: blood passes through the heart twice in one full circuit. One loop goes to the lungs, the other to the rest of the body.
- Major heart vessels: the aorta carries oxygenated blood out of the left ventricle to the body; the vena cava returns deoxygenated blood to the right atrium; the pulmonary artery takes blood to the lungs; the pulmonary vein brings it back.
- Heart valves stop blood flowing the wrong way. The tricuspid and bicuspid (mitral) valves sit between atria and ventricles, and the semilunar valves sit at the exits of the ventricles.
- Bile is made in the liver and stored in the gall bladder. It is released into the small intestine, where it emulsifies fats into smaller droplets so lipase can break them down more easily.
- The nervous system is split into the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves that connect the CNS to the rest of the body).
- Parts of the eye: the cornea and lens focus light onto the retina; the iris changes the size of the pupil to control how much light enters. The lens becomes more curved to focus on near objects — this is accommodation.
- Adrenaline is the 'fight or flight' hormone, released from the adrenal glands. It raises heart rate and breathing rate to prepare the body for sudden action.
- Pathogens are microorganisms that cause disease. The main groups are bacteria, viruses, fungi and protists. Examples: Salmonella (bacteria), measles (virus), athlete's foot (fungus) and malaria (protist).
- Malaria is caused by Plasmodium, a protist spread between humans by the bite of female Anopheles mosquitoes acting as vectors.
- Vaccines contain a weakened or inactive form of a pathogen, or part of it. They trigger white blood cells to make antibodies and memory cells, so a real infection later can be fought off quickly.
- Sex chromosomes in humans: females are usually XX and males are usually XY. A father can pass on either an X or a Y, so the father's sperm determines a baby's biological sex.
- In binomial nomenclature each species is given a two-word Latin name: the first word is the genus and the second is the species. For example, humans are Homo sapiens.
- The classification hierarchy from broadest to narrowest is kingdom, phylum, class, order, family, genus, species. A common memory hint is 'King Philip came over for good soup'.
- The carbon cycle moves carbon between the air, living things and the ground. Photosynthesis removes CO2 from the air, respiration and combustion add it back, and decomposers return carbon from dead matter to the soil and air.
- In the nitrogen cycle, nitrogen-fixing bacteria turn nitrogen gas into compounds plants can use, nitrifying bacteria convert ammonia into nitrates, and denitrifying bacteria return nitrogen gas to the air.