paper 2 Flashcards
What is the definition of homeostasis?
The regulation
of the internal conditions of a cell or organism
Why is homeostasis important?
Why is homeostasis important?
To maintain optimum conditions for enzyme
List 3 things that are controlled as part of homeostasis.
•blood glucose concentration
•body temperature
•water levels.
What is a receptor?
cells that detect stimuli
What is an effector?
Muscles or glands, which bring about responses which
restore optimum levels.
Name the two parts of the central nervous system.
Brain and spinal cord
What is the purpose of the nervous system?
The nervous system enables humans to react to their surroundings and
to coordinate their behaviour.
How are messages passed through the nervous system?
Via electrical impulses
Put these into the correct order: receptor, effector, sensory neurone, motor neurone, stimulus, response, coordinator.
stimulus, receptor, sensory neurone, coordinator, motor neurone, effector, response
What is a synapse?
gap between neurones. Messages are passed by chemical diffusion.
What is a reflex action?
Automatic and rapid actions which do not involve the conscious part of the brain.
Why are reflex actions important?
To avoid causing more damage to cells.
Write out the sequence of a reflex action.
Stimulus, receptor, sensory neurone, synapse, relay neurone, synapse, motor neurone, effector, response
Why does a synapse slow down a reflex action?
Because chemical diffusion is slower than electrical impulses
How are messages passed in the human endocrine system?
By chemical hormones in the bloodstream
Name the 6 glands involved in the endocrine system.
•• pituitary gland
•• pancreas
•• thyroid
•• adrenal gland
•• ovary
•• testes.
Compare and contrast the endocrine and the nervous system.
Hormones are slower acting, but the effects are longer lasting.
Why is the pituitary gland called the master gland?
It secretes hormones which work on other glands to stimulate the release of other hormones.
Name the organ which monitors and controls blood glucose concentration.
Pancreas
Name the hormone produced when blood glucose concentration gets too high.
insulin
Describe the sequence of events which leads to a return to normal blood glucose if concentration gets too high.
a return to normal blood glucose if concentration gets too high.
If the blood glucose concentration is too high, the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage.
Describe the sequence of events which leads to a return to normal blood glucose if concentration gets too low.
If the blood glucose concentration is too low, the pancreas
produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood
What is Type 1 diabetes?
A disorder in which the pancreas fails to produce sufficient insulin.
What is the treatment for Type 1 diabetes?
Insulin injections
What is Type 2 diabetes?
occurs when the body cells no longer respond to insulin produced by the pancreas.
What is a major risk factor for Type 2 diabetes?
Obesity
How is Type 2 diabetes treated?
A carbohydrate controlled diet and an exercise regime
Name the male reproductive hormones and describe their effects during puberty.
Male: testosterone, produced by testes, sperm production begins, voice deepens
Name the female reproductive hormones and describe their effects during puberty.
. Female: oestrogen, ovaries, menstrual cycle begins, breasts develop
What is ovulation?
Release of an egg from an ovary
How long does a mentrual cycle typically take?
Approx. 28 days
Describe the roles of FSH, LH, oestrogen and progesterone in the menstrual cycle.
FSH: causes egg to mature in the ovary. LH: causes ovulation. Oestrogen and progesterone: develop and maintain uterus lining
List 3 non-hormonal contraceptives.
condoms, copper coil, femidom, diaphragm, spermicidal gel
List 3 types of hormonal contraceptive.
Pill, mini-pill, injection, patch, hormonal IUD, implant
What is the role of hormones in hormonal contraceptives?
Hormones inhibit maturation and release of egg.
What is an IUD and how does it prevent pregnancy?
Copper IUD prevents implantation of a fertilised egg into the uterus
Apart from contraceptives describe two other ways inwhich pregnancy can be prevented.
Abstinence (not having sexual intercourse), male and female sterilisation
Where is the genetic material found in a cell?
nucleus
What is the structure of DNA known as?
Double helix
What is a chromosome?
The 3D structure that contains DNA
What is a gene?
small section of a chromosome that codes for a sequence of amino acids to make a specific protein
What is a genome?
The entire genetic material of that organism
Why is understanding the genome important?
To find genes which are linked to diseases such as cancer
What is the definition of sexual reproduction?
Reproduction using gametes
What is the definition of asexual reproduction?
Reproduction not using gametes to create an identical individual
gametes
sex cell
Name the gametes in animals and plants.
Animals= Sperm and Egg cells
Plants= Pollen and Ovule
Which type of reproduction leads to variety within offspring?
Sexual reproduction
How can you describe the offspring of asexual reproduction?
clones
What is meiosis?
Cell division producing genetically different gametes
Why is meiosis important for sexual reproduction?
Each gamete will combine with another to create a unique genome/ genotype
Describe a basic outline of what happens during meiosis
Parent cell will copy the DNA and organelles to produce 2 daughter cells. Each daughter cell will then split again to produce 4 haploid (Half DNA) gametes.
How is meiosis different from mitosis?
Mitosis produces 2 identical daughter cells but meiosis creates 4 gametes
List 3 advantages of sexual reproduction.
produces variation in offspring, meaning a survival advantage if there is an environmental change, sexual reproduction can be used to human advantage in selective breeding.
List 4 advantages of asexual reproduction
Only one parent is needed, more time and energy efficient as organisms do not need to find a mate, faster the sexual reproduction, many identical offspring can be produced in favourable conditions.
three examples of organisms which use both methods depending on the circumstances.
Malarial parasites reproduce asexually in humans, but sexually in the mosquito. Fungi reproduce asexually by spores, but also sexually to give variation. Many plants produce seeds sexually, but also reproduce asexually by runner or bulb division.
How many chromosomes in a human body cell?
23 pairs, 46 individual chromosomes
What does the 23rd pair of chromosomes determine?
Sex / gender
What are the sex chromosomes for female offspring?
XX
What are the sex chromosomes for male offspring?
XY
What is an allele?
Different forms of the same gene
List 2 things that are controlled by a single gene.
Eye colour, Natural hair colour, Skin colour, tongue rolling
What is meant by genotype and phenotype?
Genotype is the combination of alleles in an organism.
Phenotype is the observable features of an organism.
What is a homozygous genotype and what is a heterozygous genotype?
Homozygous is two copies of the same allele.
Heterozygous is different copies of the alleles
What would the phenotype be for a cc genotype for red-green colour blindness?
Sufferer of red-green colourblindness
What would the phenotype be for a Cc genotype for red-green colour blindness?
Will not have red green colourblindness
State the probability of two heterozygous parents having a homozygous recessive offspring.
25%
What is polydactyly?
Having extra digits (fingers and toes)
What is polydactyly?
dominant allele
cystic fibrosis
The build up of mucus on exchange surfaces
What causes cystic fibrosis?
recessive allele
embryo screening
Taking a sample from the embryo to determine whether it will suffer from a genetic disorder.
Describe 2 pros and 2 cons of embryo screening.
Pros:
Can evaluate the risk to embryo/mother
Parents can make an informed decision about the suffering/lifestyle of their child
Cons:
Can lead to infection and harm to embryo
Ethical implications about terminating unhealthy embryos
variation
Differences in the characteristics of individuals in a population
What is meant by phenotype?
Phenotype is the observable features of an organism
Name one characteristic which is casued by genetic inheritance alone, one that is caused by the environment and one that could be a combination of the two.
Genetic= Tongue rolling, Attached or dangling ear lobes
Both= Hair colour, Skin colour, Height, Weight
Environment=Accent, language
What gives rise to new variants within a population
mutation
Do all mutations lead to changes in the phenotype of an organism
Not if the mutation occurs on an area of the DNA that doesnot code for a protein.
