paper 2 biology

• Luteinizing hormone (LH): is also secreted by pituitary gland and causes mature egg to be released from ovary
• Follicle stimulating hormone (FSH) is secreted by the pituitary gland. It causes an egg to mature in an ovary and it stimulates ovaries to release hormone oestrogen
• Testosterone is male sex hormone which causes development of secondary sexual characteristics such as deepening voice and growth of facial hair
• Progesterone is a hormone secreted by ovaries. It maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy
• Oestrogen is secreted by the ovaries. It stops FSH being produced - so that only one egg matures in a cycle and it stimulates the pituitary gland to release hormone LH.
• Homeostasis is the control of internal conditions within set limits
• Homeostasis: the maintenance of a constant internal environment
• Hormones: a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs
• Gland: Adrenal gland Hormone: AdrenalineFunction: Prepares body for vigorous action
• Gland: Pancreas Hormone: Insulin Function: Reduces concentration of glucose in blood
• Gland: Testis Hormone: Testosterone Function: Causes development of male sexual characteristics
• Gland: Ovary Hormone: Oestrogen Function: Causes development of female sexual characteristics
• Gland: Pituitary Hormone: Growth hormone Function: Stimulates growth of bones and muscles
• Gland: Thyroid Hormone: Thyroxin Function: Controls rate at which cells use energy
• Disadvantages of asexual reproduction:

  • No variation
  • Harmful genes transferred
  • Overcrowding- fighting for food
• Advantages of asexual reproduction:

  • Fast: no need to find mate, fertilise etc.
  • Good characteristics are kept
• Asexual reproduction: the process resulting in the production of genetically identical offspring from one parent.
• Disadvantages of sexual reproduction:

  • Takes lots of time and energy
  • Good characteristics can be lost
  • Energy on improving appearances or pollen volume for pollination (plants)
• Advantages of sexual reproduction:

  • Produces genetically different offspring
  • don’t all die from change in the environment
• Nuclei of gametes are haploid and that the nucleus of a zygote is diploid
• Fertilisation: the fusion of gamete nuclei
• Sexual reproduction: process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote and the production of offspring that are genetically different from each other
• Mitosis: cell division where the number of chromosomes remains constant, used by somatic cells to produce new body cells
• Meiosis: cell division where the number of chromosomes halves, produces gametes with half the number of chromosomes as normal body cells
• Gametes: sex cells produced during meiosis
• Homologous pairs: pairs of chromosomes containing alleles for the same gene
• Homologous pairs: two chromosomes containing identical genes but not necessarily the same alleles
• Zygote: fertilised egg formed when sperm fuses with an ovum
• Alleles: alternative forms of a gene
• Alleles: alternative forms of genes at the same locus on homologous chromosomes
• Dominant allele: an allele which is expressed when it is present in one or both copies of a pair of alleles
• Recessive allele: an allele which is only expressed if it is present in both copies of a pair of alleles
• Alleles: alternative forms of a gene at a specific locus on a homologous pair of chromosomes
• Genotype: genetic make-up of an organism
• Phenotype: physical characteristics of an individual
• Phenotype: observable characteristics of an organism, determined by its genotype and environment
• Genotype: genetic makeup of an individual, determined by their alleles