Aqa biology foundation paper 2

• Homeostasis is the term given to an organism's ability to regulate internal conditions even when external conditions change
• Crucial chemical reactions involving enzymes can happen at an optimum rate
• Our bodies work hard to regulate blood glucose concentration, temperature, and water levels
• The nervous system consists of the CNS (central nervous system) - the brain and spinal cord, and the PNS (peripheral nervous system) - the nerves that go through the rest of the body
• A receptor, for example, skin, detects a change due to a stimulus like a hot hob
• A reflex is when the signal bypasses the brain and goes straight through the spine to the affector, known as a reflex arc
• Glands can also be effectors which produce specific chemicals your body needs depending on the situation
• Investigating reaction times can be done by holding the bottom of a ruler between a person's finger and thumb and dropping it without warning
• Water and nitrogen balance are triple only
• Reproduction: Menstruation occurs in females after puberty
• FSH (follicle stimulating hormone) causes an egg to mature in the ovary
• Estrogen causes the uterus lining to thicken and inhibits the production of FSH
• Progesterone maintains the uterus lining
• Contraception options include pills, injections, implants, condoms, diaphragms, IUDs
• Adrenaline increases heart and breathing rate in stressful situations
• Thyroxin controls metabolic rate
• Plants have hormones like gibberellins, ethene, and auxins
• Gibberellins cause seed germination and promote flowering and fruit size
• Ethene induces ripening of fruits
• Auxins control shoot and root growth
• Orins cause phototropism in shoots and geotropism in roots
• Meiosis is the process by which gametes are produced
• Variation occurs in offspring through meiosis and mitosis
• Sexual reproduction leads to variation which can result in organisms better suited to their environment
• Asexual reproduction results in genetically identical offspring, creating a clone of the parent
• Some organisms can reproduce both sexually and asexually
• Genome is the term given to all the genetic material in an organism, stored in DNA
• A gene is a section of DNA that codes for a specific protein
• The Human Genome Project completed its initial goal in 2003, mapping out what every gene is responsible for coding
• Genotype is the term given to the genetic code stored in DNA, while phenotype is how that code is expressed in characteristics
• Nucleotides are the monomers between the two strands of DNA, made from a sugar and phosphate group, with four types: A, T, C, and G
• Every three bases in DNA code for an amino acid
• The sequence in DNA is copied by mRNA, which is then taken to a ribosome in the cell where amino acids are connected in the order needed to make a protein
• Harmful mutations can change a gene so much that it results in a protein being synthesized that doesn't function properly
• Some DNA doesn't directly code for proteins but influences how other genes are expressed, known as epigenetics
• Characteristics can be controlled by one gene (e.g., color blindness) or multiple genes, with dominant and recessive alleles affecting expression
• Human DNA is contained in 23 pairs of chromosomes, with one pair determining sex (XX for female, XY for male)
• Variation in organisms is a result of genes inherited from parents and environmental factors
• Epigenetics shows that DNA can respond to the environment by turning genes on and off as needed
• Bacterial resistance is evidence of Darwinian evolution, where mutations lead to increased resistance to antibiotics