BIOLOGY EDEXCEL IGCSE DOUBLE AWARD Exit Exam With Complete Questions And Correct Actual Answers.

Physical appearance of an organism (e.g. blue eyes) - correct answer Phenotype Genotype - correct answer The sets of genes (alleles) that an organism possesses (e.g. Bb) Allele - correct answer A different version of a gene Heterozygous - correct answer When the two alleles are different (e.g. Bb) Homozygous - correct answer When two alleles are identical (e.g. BB or bb) Dominant - correct answer Allele which controls the characteristic whenever present Recessive - correct answer Allele whose characteristic only shows up when it is present on both chromosomes. Co-dominance - correct answer When two alleles have equal dominance (they will both be expressed). DNA molecule - correct answer Two strands coiled to form a double helix, the strands being linked by a series of paired bases. Bases - correct answer Adenine (A) - Thymine (T) and Cytosine (C) - Guanine (G) Diploid number of chromosomes in humans - correct answer 46 Haploid number of chromosomes in humans - correct answer 23 Nucleotide - correct answer The "backbone" of the DNA strands, a single nucleotide contains one of the 4 bases, a deoxyribose sugar and a phosphate group. DNA replication (6) - correct answer 1) Hydrogen bonds break (DNA helices enzyme) 2) Double helix unwinds to 2 separate strands 3) Each strand attracts new nucleotide 4) Nucleotides line up according to the base pairing rule (C-G, A-T) 5) The enzyme polmerase joins up the nucleotides to form 2 identical DNA molecules 6) Each new DNA molecule contains one strand from the parent DNA and one new complementary strand. Mutation - correct answer A random change in the DNA of a cell. Chromosome - correct answer Contains one double stranded DNA molecule. The DNA is folded and coiled around proteins called histones so it can fit into a small space. Mitosis definition - correct answer The cell division of normal body cells. Required for growth and repair of tissues, asexual reproduction. Mitosis process (5) - correct answer 1) The DNA of each chromosome is replicated to form two identical sister-chromatids. 2) The chromatids are attached to each other at the centromere. The membrane around the nucleus breaks down. 3) The chromosomes line up at the centre of the cell and cell fibres pull them apart. 4) The centromere splits and the two sister chromatids move to the opposite ends of the cell. 5) Two new nuclei form around the two sets of chromosomes, cytoplasm divides. Meiosis definition - correct answer A type of cell division that results in male/female gametes. Required for the production of sex cells. Meiosis process (4) - correct answer 1) 4 chromosomes are in a parent cell (2 homologous pairs) 2) Each chromosome copies itself (2 chromatids) and line up in pairs. 3) First cell division: one chromosome from each homologous pair goes into each daughter cell. 4) Second division: Chromatids separate and one from each chromosome ends up in a daughter cell. Evolution definition - correct answer A gradual change over time in the range of organism on earth. Natural selection definition - correct answer The mechanism by which new species arise. Struggle for existence - correct answer Many offspring are produced yet population stays the same size because there is a competition for resources so some die. Survival of the fittest - correct answer If some offspring survive and others die, the ones best suited to the environment will survive to reproduce. Evolution by natural selection (5) - correct answer 1) Variation due to advantageous allele 2) Competition for resources 3) Variety with advantageous allele better adapted to compete, so survive. 4) If they survive, then there is a greater chance of passing on alleles through reproduction. 5) Greater proportion of individuals in the next generation will have the advantageous allele, increasing chance of survival, over time becoming the most common in the population. Anthers - correct answer Site of pollen grain production. Part of the stamen. Carpel - correct answer The female reproductive organs of a plant - collective term for the style, stigma and ovary. Fertilisation - correct answer The fusion of the nuclei of the male and female gametes Filament - correct answer The long stalk that connects the anther to the rest of the plant. Also part of the stamen. Ovary - correct answer Contains the ovule, which encloses the female gamete. It's wall may become part of the fruit on fertilisation Ovule - correct answer Site of ovum production. Found in the ovary. Ovum - correct answer Female gamete Pollen grain - correct answer Male sex cell or gamete. Pollination - correct answer The transfer of pollen from the anther to the stigma of a plant of the same species. Stamen - correct answer The male reproductive organ of a plant - collective term for the anther and filament. Stigma - correct answer Part of the female reproductive organs. Surface on which the pollen grains containing male gametes may be disposed Style - correct answer The part of the carpel that joins the stigma to the ovary. Holds stigma in place Nectary - correct answer Produces nectar- a sugary liquid for pollinating insects Sepal - correct answer protects the flower from drying out and fungal attacts Cross-pollination - correct answer Pollen transfer between different flowers of the same species. Involves genetic variation but is risky as a vector (carrier) is required. Self-pollination - correct answer involves pollen transfer between the stamen and stigma of the same flower. It is less risky and ensures survival of species but limits genetic variation. Pollen Tube - correct answer Grows down the style from the pollen grain and acts as a channel to deliver the male gamete to the ovum. Seed Germination - correct answer Requires water, oxygen and a good temperature Seed dispersal - correct answer Allows plants to colonise new areas. There's less competition for for resources and it stops overcrowding Runners - correct answer Used by plants for Asexual reproduction Aorta - correct answer Carries oxygenated blood from the heart to the body Pulmonary artery - correct answer Carries deoxygenated blood from the heart to the lungs. Pulmonary vein - correct answer Carries oxygenated blood from the lungs to the left atrium. Left ventricle - correct answer Chamber that pumps oxygenated blood out to the body through the aorta - thicker muscle wall Vena cava - correct answer Large vein that carries deoxygenated blood into the right atrium Vein - correct answer Carry deoxygenated blood to the heart with the exception of the pulmonary vein. They are less muscular than arteries as the blood is lower pressure. They contain valves to prevent backflow. Capillaries - correct answer Blood is not under great pressure . The walls are only one cell thick to allow exchange of materials. They do not contain valves and carry both oxygenated and deoxygenated Arteries - correct answer Carry blood away from the heart with the exception of the pulmonary artery. They are muscular and the blood is higher pressure. They DONT contain valves. Hepatic portal vein - correct answer M - MRSHGREN - correct answer movement, for all or part of the organism R - MRSHGREN - correct answer respiration, getting energy from food S - MRSHGREN - correct answer Sense, changes in the surroundings H - MRSHGREN - correct answer Homeostasis, controlling their internal environment G - MRSHGREN - correct answer growth, development R - MRSHGREN - correct answer reproduction, producing offspring E - MRSHGREN - correct answer excretion, removing waste products N - MRSHGREN - correct answer nutrition, needing of food Test for glucose - correct answer 1. Warm water bath 2. Benedict solution turns brick red Test for Starch - correct answer iodine solution turns blue or black. Definition of enzyme - correct answer Biological catalysts that control all the reaction in a cell What happens when the active site stops the enzyme working? - correct answer Denatures What is Aerobic respiration? - correct answer Respire that requires oxygen Equation for Aerobic respiration - correct answer Glucose + Oxygen = Carbon dioxide + Water + Energy What is Anaerobic respiration? - correct answer Respire that doesn't requires oxygen Equation for Anaerobic respiration - correct answer Glucose = Ethanol + Carbon dioxide + some energy Test for carbon dioxide - correct answer bubbles in limewater, turns cloudy Definition of diffusion - correct answer movement of particles from an area of high concentration to an area of lower concentration. It is caused by random movement of particles. Definition of Osmosis - correct answer Only water moves across a partially permeable membrane from an area of high concentration to a low concentration Definition of active transport - correct answer Substances are moved against a concentration gradient or across a selectively permeable membrane. Uses energy produced by cellular respiration All specialized cells in order - correct answer Organelles, cells, tissues, organs, organ systems Features of Plants - correct answer - multicellular - carry out photosynthesis Features of Animals - correct answer - Multicellular - cannot carry out photosynthesis Features of Fungi - correct answer - Can be multicellular or unicellular - cannot carry out photosynthesis Features of Protoctists - correct answer - Can be unicellular or multicellular - can carry out photosynthesis Features of Bacteria - correct answer - Single-celled organisms - some can carry out photosynthesis Trachea - correct answer Tube with incomplete rings of cartilage carries air to lungs bronchus - correct answer carries air to lung bronchioles - correct answer carry air to lungs alveoli - correct answer tiny air sacs adapted for gaseous exchange diaphragm - correct answer sheet of muscle with a fibrous middle part which is domed ribs - correct answer bones that protect and ventilate lungs internal intercostal muscles - correct answer pull ribs down and in external intercostal muscles - correct answer pull ribs up and out The advantages of alveoli - correct answer 1. A large surface area 2. A rich blood supply (capillaries) 3. short diffusion distances The effect of tobacco - correct answer 1. cilia are destroyed so dirt and bacteria are not removed 2. the walls of the alveoli are damaged 3. lung cancer 4. carbon monoxide binds with haemoglobin in blood cause lack of oxygen level 5. affects the circulatory system and increase the risk of heart attacks and strokes Amylases breaks down - correct answer starch in to maltose Maltase breaks down - correct answer Maltose into glucose protease breaks down - correct answer protein into amino acids lipase breaks down - correct answer Lipid into fatty acids and glycerol What are proteins - correct answer They are long chains of amino acids found in foods What are lipids - correct answer they are made up of carbon, hydrogen, and oxygen Definition of absorption - correct answer The products of digestion are absorbed into your bloodstream in the small intestine. Definition of Assimilation - correct answer The digested food products are absorbed into the cells of the body by diffusion