Unit 2 Flashcards
What word is used to describe cells that have an adapted structure to carry out a particular function?
Specialised
What is
a) a tissue
b) an organ
c) a system
a) a group of cells that are specialised to perform a particular function
b) a group of tissues that perform the same function
c) a group of organs
What are stem cells and what do they do?
They are non-specialised animal cells that can divide and become specialised.
They carry out growth and repair
What name is given to the part of a plant that produces non-specialised cells?
meristem
Why is internal communication needed for a multicellular organism to survive
Cells in a multicellular organism don’t work independently
What makes up the nervous system?
1) CNS ( central nervous system)
2) nerves
What is central nervous system?
brain and spinal cord
What are the three main parts of the brain and what do they do?
cerebellum - controls balance and coordination
cerebrum - controls thought and personality
medulla - controls breathing and heart rate
What are the three types of neurons and what do they do?
sensory neurons - carry an electrical impulse from sensory receptors to the spinal cord and brain
inter neurons - carry electrical impulses from one part of the CNS to another
motor neuron - carry electrical impulses from one part of the CNS to make a response happen eg. muscle move.
How do electrical impulses get transferred from one neuron to another?
By chemical messages travelling across synapses
List the three types of neuron in a reflex arc
sensory neuron
relay neuron
motor neuron
What is a reflex arc?
a rapid pathway that goes through the spinal cord but does not pass through the brain
What is a reflex?
A rapid response that happens without conscious thought
Give two examples of reflexes
Any 2 from:
blinking, response to pain, iris response to light, response to touching something hot, sneeze and knee-jerk.
What name is given to chemical messengers in the blood?
hormones
Where do hormones come from?
endocrine glands
Why do some hormones only work on certain tissues?
Hormones only work on tissues that have receptors for them
Which hormone is released when blood glucose levels are higher than normal?
insulin
Which hormone is released when blood glucose levels are lower than normal?
glucagon
How is glucose stored in the liver?
As glycogen. This is long chains of glucose molecules joined together.
How does insulin lower the blood glucose level?
It causes glucose to be converted into glycogen in the liver
How does glucagon raise the blood glucose level?
It causes glycogen to be converted into glucose in the liver
Which organ releases insulin and glucagon?
pancreas
Which two hormones control blood glucose levels?
insulin and glucagon
What name is given to cells that contain two copies of each chromosome?
diploid
What name is given to cells that contain only one copy of each chromosome?
Where are these found?
Haploid
The gametes are haploid cells so found in ovaries or testes
What are the gametes?
a) in animals
b) in plants
a) egg and sperm cells
b) pollen and ovule cells
Where are gametes made in animals?
male - testes
female - ovary
Where are gametes made in plants?
Male - pollen made in anther
female - ovule made in ovary
What is fertilisation?
Fusion of two haploid gametes to make a diploid zygote
What is a zygote?
The new cell with 2 copies of each chromosome made by fertilisation.
or
The cell made when male and female gametes join.
What is discrete variation?
Differences caused by the presence or absence of a gene or group of genes
What is continuous variation?
Differences caused by complex interactions of genes and the environment
Give an example of discrete variation in humans
tongue rolling (you can either do it or you can’t)
blood group - A, B, AB r O
Give an example of continuous variation in humans
height (can take a range of values)
weight
hand span or any other body dimension
What causes genetic variation?
The combination of genes from two parents (sexual reproduction)
What is the phenotype of an organism?
Its physical appearance and characteristics
What is the genotype of an organism?
The set of alleles it has inherited
What are alleles?
Different forms of the same gene
E.g. the gene for eye colour has an allele for blue and an allele for brown
What does homozygous mean?
Has the same two alleles of a gene e.g. RR or rr
What does heterozygous mean?
Has two different alleles of a gene e.g. Rr
What name is given to an allele that will only to be expressed if it is homozygous?
recessive
What name is given to allele that is expressed when heterozygous?
dominant
In genetics, what are P1, F1 and F2?
P1 - the parents
F1 - the offspring from the P1 parents (children)
F2 - the offspring from F1 generation (grandchildren)
How can some people have the allele of a gene that causes disease yet not get the disease?
The disease allele may be recessive. It is therefore possible to have the allele but it is not expressed - the person would be a carrier.
Why are the predicted ratios of genetic inheritance not always achieved?
The combination of genes is a random event.
With big enough samples the statistical ratios are usually achieved but with small samples this is not the case.
List seven structural parts of a plant leaf.
upper epidermis, palisade mesophyll, spongy mesophyll, vein, lower epidermis, guard cells, stomata
What are the tiny holes in leaves that allow water to evaporate out called?
Stomata
What do the guard cells on a leaf do?
Open and close the stomata to prevent water loss at night.
How does water travel up through a plant?
Transpiration.
Water evaporating from the leaves pulls the column of water up through the xylem.
What do xylem vessels do?
transport water and minerals
How does water enter plants?
Through the roots. Root hairs increase the surface area so they can absorb lots of water.
Describe the structure of xylem
It is long tubes of dead cells that contain lignin.
What is the role of lignin in xylem cells?
It makes the xylem strong and waterproof
Why do leaves need water?
For the mesophyll cells to carry out photosynthesis
How is sugar transported around a plant?
In phloem cells
List two differences between xylem and phloem
xylem carries water
phloem carries sugar
xylem cells are dead
phloem cells are alive
How do phloem cells stay alive when they don’t have much cytoplasm?
They have companion cells which carry out many of the activities the phloem needs to stay alive.
How are nutrients, oxygen and carbon dioxide transported around the body in mammals?
In blood
Describe the flow of blood through the heart
From body to right atrium, to right ventricle, to lungs.
From lungs to left atrium to left ventricle to body.
What do the valves in the heart do?
Prevent the blood flowing backwards
Which blood vessel delivers blood from the body to heart?
vena cava
Which blood vessel carries blood away from heart to the lungs?
pulmonary artery
Which blood vessel carries blood from the lungs back to the heart?
pulmonary vein
Which blood vessel carries blood from the heart to the body?
aorta
Describe where the valves in the heart are.
On both sides of the heart
1) between the atrium and ventricle
2) between the ventricle and blood vessel
Which blood vessels supply the muscle of heart with blood so it can keep beating?
coronary arteries
Describe four differences between arteries and veins.
Arteries - thick muscular walls
veins - thinner walls
arteries - high pressure
veins - low pressure
arteries - narrow central channel
veins - wide central channel with valves
arteries - carry blood away from the heart
veins - carry blood towards the heart
Which characteristics of capillaries allows them to exchange materials with tissues and organs?
They have a large surface area from forming networks.
They are very thin walled to allow substances in and out.
How is oxygen carried in the blood?
In red blood cells.
Oxygen attaches to haemaglobin to make oxyhaemaglobin
How are red blood cells specialised to carry oxygen?
They have no nucleus, have a biconcave shape and contain haemoglobin.
Which part of the lungs carries out gas exchange?
alveoli
What three factors make alveoli good at gas exchange?
large surface area
thin walls
good blood supply
How are the main airways kept open?
Rings of cartilage
How are the lungs kept clean?
Mucus traps dirt and microorgansims then cilia (little hairs) move this up and out of the lungs
What name is given to the way food is moved through the gut by a wave of muscle contractions?
peristalsis
What makes the small intestine good at absorbing and amino acids?
It has villi (finger-like bits sticking out) that increase the surface area. It has thin walls and a good blood supply.
Which part of the digestive system absorbs fatty acids and glycerol?
Lacteals which are inside each villi in the small intestine.
What do fatty acids and glycerol get taken to from the small intestine?
the lymphastic system
Which cells in the blood are involved in destroying pathogens?
White blood cells
What are the two types of white blood cells and what do they do?
- Phagocytes - engulf pathogens
2. Lymphocytes - produce antibodies which destroy pathogens.
