biology b1

• sperm adaptations

  • Streamlined head
  • Long tail
  • Lots of mitochondria to provide energy
• nerve cell adaptations

  • Long to cover more distance
  • Has branched connections to connect in a network
  • Long and contain lots of mitochondria for energy
• muscle function

  • To contract quickly
• root hair adaptation

  • A large surface area to absorb more water
• phloem

  • Transports substances around the plant
  • Cells are long and joined end-to-end
  • Pores to allow cell sap to flow
• xylem

  • Transports water through the plant
  • Hollow in the centre
  • Tubes are joined end-to-end
• The purpose of sperm is to get the male DNA to the female DNA
• The purpose of nerve cells is to send electrical impulses around the body
• The purpose of muscle cells is to contract quickly
• The purpose of root hair cells is to absorb water from the soil
• The purpose of phloem is to transport substances around the plant
• The purpose of xylem is to transport water through the plant
• Osmosis and Potato Practical

  . Independent variable - concentration.

  • Dependent variable - change in mass.

  . Control variable - volume of solution, temperature, time, surface area of the potato.

  The potato in the sugar solution will lose water and so will have less mass at the end; the potato in the pure water solution will gain water.
• Bacterial Cells

  Bacterial cells do not have a true nucleus, they just have a single strand of DNA that floats in the cytoplasm. They contain a plasmid.
• Embryonic stem cells are undifferentiated cells, they have the potential to turn into any kind of cell.

  Adult stem cells are found in the bone marrow, they can only turn into some types of cells e.g. blood cells.

  Uses of stem cells:

  • Replacing faulty blood cells;
  • making insulin producing cells;
  • making nerve cells.
• Some people are against stem cell research.

  For Stem Cell Research

  Curing patients with stem cells - more important than the rights of embryos.

  They are just using unwanted embryos from fertility clinics, which would normally be destroyed.

  Against Sten cells

  Embryos are human life

  Scientists should find other sources of stem cells.
• In plants, stem cells are found in the meristem.

  These stem cells are able to produce clones of the plant. They can be used to grow crops with specific features for a farmer, e.g. disease resistant.
• The alveoli are where gas exchange takes place.

  They have a large surface area, moist lining, thin walls and a good blood supply.
• Millions of villi line the small intestine increasing the surface area to absorb more digested food.

  They are a single layer of cells with a good blood supply.
• The surface of the leaf is flattened to increase the surface area for more gas exchange by diffusion.

  Oxygen and water vapour diffuse out of the stomata. Guard cells open and close the stomata, controlling water loss.
• Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.
• Cell membranes are semi-permeable, only small molecules can get through.
• Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher concentration to a region of lower concentration.
• Active transport is the movement of substances against the concentration gradient. This process requires energy from respiration.
• differentiation

  the process of cells becoming specialised
• sub cellular structures only found in plant cells

  vacuole

  cell wall

  chloroplasts
• 3 stages of mitosis:

  -dna replication and growth (2 copies of each cromosome x pattern)

  -mitosis (one set of each chromosomes pulled to each end of the cell)

  -cell division to form 2 identical cells
• mitosis is asexual reproduction and produces 2 genetically identical daughter cells
• mitosis takes place when an organism grows or repairs itself (e.g broken bone)