Unit 2 - Multicellular Organisms

• How are new cells made?


  The cells grow and divide.
• Why do cells need to carry out cell division?


  To make cells for growth and repair.
• What are the steps involves in Mitosis?


  1. Chromosomes shorten and thicken so they can be seen

  under a microscope.

  2. The chromosomes line up along the equator of the cell.

  3. The spindle fibres pull the chromatids apart to opposite

  poles of the cell. The separated chromatids are now known

  as chromosomes.

  4. The nuclear membrane reforms.

  5. The cytoplasm divides. Two new identical daughter cells are

  formed.
• What are Stem Cells?


  A stem cell is an unspecialised cell which can divide and have the potential to become different types of cells.
• What are stem cells for?


  Growth and repair.
• What are the two things that stem cells can do?


  Self Renew and Become Specialised.
• What are the two types of stem cells?


  1. Embryonic stem cells.

  - Found only in embryos.

  - Can specialise into any human cell.

  2. Tissue stem cells.

  - Only found in adults.

  - Can specialise into a few different cells.
• What is the order of increasing level of organisation in a multicellular organism?


  Tissue, Organ, Organ System
• What does the Nervous System consist of?


  The Central Nervous System and other Nerves.
• What does the Central Nervous System consist of?


  Brain and Spinal Cord
• What is the function of the Cerebrum?


  Memory and Muscle Movement
• What is the function of the Cerebellum?


  Balance and Coordination
• What is the function of the Medulla?


  Breathing and Heart Rate
• What are the three types of neurons?


  Sensory, Inter, Motor.
• What do electrical impulses do?


  Carry messages along neurons.
• What is the junction between neurons called?


  Synapse.
• What transfers the nerve impulse over the synapse?


  Chemicals.
• Describe how the stimulus is detected and how the message is transferred into and across the spinal cord.


  1. Detected by receptors.

  2. Sent by chemical impulse.

  3. Message goes from sensory to inter neuron.

  4. Across synapse or chemical transfer between neurons.
• What are Reflex Arcs?


  They are a special type of pathway in the nervous system. They avoid going to the brain and so the response is automatic and quicker.
• Why are Reflex Arcs needed?


  To protect the body from injury.
• Describe the reflex arc.


  1. Sensory receptors in the skin detect stimuli.

  2. The nerve impulse is carried from the sensory neurons to the

  relay neurons.

  3. The relay neuron passes the nerve impulse to the motor

  neuron.

  4. The motor neuron brings about a response from the effector.
• What is a type of gland that releases hormones into the bloodstream?


  Endocrine Gland.
• Why is it that hormones only target certain tissues?


  The target tissues have cells with receptor proteins for the hormones so that only specific tissues are affected.
• What is the role of insulin?


  To regulate blood sugar concentration by promoting the conversion of glucose into glycogen. Insulin is released when glucose concentrations in the blood are high.
• How is glucose stored in the body?


  As glycogen.
• What is the function of glucagon?


  To promote the conversion of glycogen to glucose. Glucagon is released when glucose concentrations in the blood are low.
• What is the role of the pancreas.


  Produces insulin and glucagon.
• What is the role of the liver?


  Involved in the regulation of blood glucose levels.
• Describe how blood glucose is returned from low to normal levels in the human body.


  When blood glucose is low, the pancreas makes the hormone glucagon and releases it into the bloodstream. This hormone travels in the blood to the liver. The liver is the target tissue for glucagon as its cells have specific receptor proteins. In the liver, glycogen is broken into glucose. The glucose is released into the blood, causing glucose levels to increase.
• What is a Haploid Cell?


  A cell with only one set of chromosomes.
• What is a Diploid Cell?


  A cell with two sets of chromosomes.
• What is Fertilisation?


  Fertilisation is the fusion of the nuclei of the two haploid gametes to produce a diploid zygote, which divides to form an embryo.
• What is a gamete?


  Sex cell.
• What is the male gamete in animals and where is it produced?


  Sperm, Testis.
• What is the female gamete in animals and where is it produced?


  Egg, Ovary.
• What is the male gamete in plants and where is it produced?


  Pollen, Anther.
• What is the female gamete in plants and where is it produced?


  Ova, Ovary.
• What is Discrete Variation?


  A result of single gene inheritance and the measurements fall into distinct groups. For example, hair colour, eye colour and blood type.
• What is Continuous Variation?


  A result of polygenic inheritance and there is a range of values between a maximum and a minimum. For example, height, weight and handspan.
• What is a gene?


  A unit of genetic information.