Multicellular organisms - Flashcards
What is transpiration?
The process of water moving through a plant and its evaporation through the stomata
What are the structures and processes involved as water moves through the plant from the soil to the air?
Water moves from the soil into the root hair by osmosis.
Water then moves by osmosis from the root hair cell to the xylem in the root.
Water then travels up the xylem in the stem.
Water then moves by osmosis from the xylem to the spongy mesophyll in the leaf.
Water then evaporates from the spongy mesophyll into the moist airspace inside the leaf.
Water vapour then moves by diffusion from the air space in the leaf out through the stomata into the air.
What can external factors do?
Increase or decrease the rate of transpiration. eg light intensity, temperature, wind speed, humidity
How does light affect the rate of transpiration?
In bright light transpiration increases, and the stomata open wider to allow more carbon dioxide into the leaf for photosynthesis
How does temperature affect the rate of transpiration?
Transpiration is faster in higher temperatures, evaporation and diffusion are faster at higher temperatures
How does wind speed affect the rate of transpiration?
wind speed is faster in windy conditions, water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf.
How does humidity affect the rate of transpiration?
Transpiration is slower in humid conditions, diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air.
How does leaf surface area affect the rate of transpiration?
Higher leaf surface area leads to faster transpiration, a larger leaf has more stomata, so more water will be evaporating and diffusing away from the plant. Plants may lose leaves at times of water shortage to combat this.
In mammals what does the blood contain?
Plasma, red blood cells and white blood cells
What does blood transport?
Nutrients, oxygen and carbon dioxide.
How are red blood cells specialised to carry oxygen?
They are biconcave in shape, have no nucleus and contain haemoglobin
How do red blood cells transport oxygen efficiently?
In the form of oxyhaemoglobin
What is the chemical formula for the production of oxyhaemoglobin
oxygen+haemoglobin= oxyhaemoglobin
What are white blood cells part of and what are they involved in?
They are part of the immune system and they are involved in destroying pathogens.
What are pathogens?
Disease-causing micro-organisms.
What are the two main types of blood cells involved in destroying pathogens?
Phagocytes and lymphocytes
What do phagocytes do?
They carry out phagocytosis by engulfing pathogens.
Describe the process of phagocytosis
When a phagocyte detects a pathogen it captures it by flowing its cell membrane around the pathogen and engulfing it in a vacuole in its cytoplasm. The trapped pathogen is then digested using enzymes.
What do some lymphocytes do?
They produce antibodies which destroy pathogens.
What is each antibody specific to?
A particular pathogen.
Describe the sequence of events in mitosis.
Each chromosome makes an identical copy of itself- the two copies are called chromatids.
The chromatid pairs line up at the equator of the cell.
Spindle fibres now pull the pairs of chromatids apart so that only one copy of each chromosome moves to each pole of the cell.
Nuclear membrane forms around each set of chromosomes at the poles.
After the two nuclei have formed, the cytoplasm divides and 2 separate diploid cells are formed.
What is an equator?
the region in the middle of the cell where the chromatid pairs line up before they are separated
What are spindle fibres?
strands of protein that the cell uses to separate the chromatid pairs from the equator to the poles
What does mitosis provide and maintain?
provides new cells for growth and repair of damaged cells and maintains the diploid chromosome complement.
What are diploid cells?
Cells that have two matching sets of chromosomes, which are replicated during mitosis
What are stem cells?
unspecialised cells that can divide in order to self-renew
What do stem cells have the potential to do?
become different types of cell
What are stem cells involved in?
growth and repair
Where can stem cells be obtained from?
the embryo at a very early age
where can tissue cells be found?
in the body, throughout life
what are stem cells used for?
therapies such as bone marrow transplants. skin grafts and cornea repair.
What does the specialisation of cells lead to?
the formation of a variety of cells, tissues and organs.
Describe multicellular organisms
multicellular organisms have more than one cell type and are made up of tissues and organs.
What do organs do?
perform different functions
Describe cells in organs.
They are specialised for their functions.
What is the hierarchy that exists?
cells-tissues-organs-systems
Give an example of a specialised plant cell.
xylem vessel-hollow tube, wall strengthened by lignin-support and water transport
Give an example of a specialised animal cell.
cheek epithelium-flat irregular shape-protection of mouth lining
What can a response to a stimulus be?
a rapid action from a muscle or a slower response from a gland
What does the nervous system consist of?
the CNS and other nerves
What does the CNS consist of ?
brain and spinal cord
What is the cerebrum?
the large folded area of the brain and is responsible for conscious thoughts, reasoning, memory and emotions
what is the cerebellum?
found at the rear of the brain below the cerebrum and controls balance and coordinated movement
what is the medulla
the medulla is found at the top of the spinal cord and transmits electrical impulses to the heart and lungs to control heart rate and breath rate
what do electrical impulses do
carry messages along neurons
How do messages get transported?
chemicals transfer these messages between neurons, at synapses
what are the three types of neuron?
sensory, inter and motor
what do receptors do?
detect sensory input/stimuli
What do sensory neurons do?
pass the information to the CNS
What do inter neurons do?
they operate within the CNS and process information from the senses that require a response
what do motor neurons do?
enable a response to occur at an effector
What is a reflex arc?
Reflex reactions are controlled by the reflex arc. The messages may be passed directly from a sensory neuron, via an inter neuron to a motor neuron for a very rapid response
what do reflexes do?
protect the body from harm
what do endocrine glands do?
release hormones into the bloodstream
what are hormones?
chemical messengers
why are only some body tissues affected by specific hormones
target tissues have cells with complementary receptor proteins for specific hormones. Only cells that have the appropriate complementary receptor will be affected by a specific hormone.
Why is blood glucose concentration regulated?
to ensure that respiration is releasing energy in the form of ATP at the correct rate
What are insulin and glucagon?
hormones released by the pancreas in order to to control blood glucose concentration. Both hormones trigger the action of enzymes in the liver that control the rate of conversion of glucose into glycogen or back again.
What happens when the concentration of glucose is too high?
the hormone insulin is released by the pancreas into the bloodstream. This insulin triggers liver enzymes to convert glucose into glycogen. This lower the concentration of glucose in the blood.
What happens when the concentration of glucose is too low?
the hormone glucagon is released by the pancreas into the bloodstream. When glucagon is detected by the liver cells they convert stored glycogen to glucose and this raises the blood glucose concentration.
What are cells?
diploid (except gametes)
what are gametes?
haploid
What are the two types of gametes?
egg and sperm
describe an egg
they are produced in the ovaries
describe a sperm
sperm are continuously produced in the testes of adult male mammals
what is fertilisation
the fusion of the nuclei of two haploid gametes to produce a diploid zygote, which divides to form an embryo
what contributes to variation within a species
combining genetic material from two parents
compare discrete variation and continuous variation
discrete variation is variation that tends to have phenotypes that fall into distinct groups (single gene inheritance) whereas continuous variation shows a wide range of values falling within a maximum or a minimum (polygenic inheritance)
What is a gene?
a gene is a location on a chromosome where a section of DNA contains the codes for a particular protein.
What is an allele?
alleles are different forms of a gene.
What is a phenotype?
The organisms physical appearance
What does the term ‘dominant’ mean?
A dominant allele always shows in the phenotype, even if the individual only has one copy of the allele.
What does the term ‘recessive’ mean?
A recessive allele only shows if the individual has two copies of the recessive allele.
What does the term ‘homozygous’ mean?
Individuals who are homozygous carries two different alleles.
What does P mean?
used to indicate the original parents in the cross
What does F1 mean?
an f1 generation (or filial 1 hybrid) is the first generation of offspring of the parent types
what does F2 mean?
an f2 generation is the second filial generation, which is comprised of offspring resulting from a cross of the members of f1 generation
What are the plant organs?
roots, stems and leaves
Be able to label a leaf structure diagram.
What parts of the plant are involved in water transport?
root hairs, xylem vessels, spongy mesophyll, guard cells and stomata
How do water and minerals enter the plant?
through root hairs and they are transported in dead xylem vessels
Describe the structure of xylem vessels
Xylem vessels consist of dead cells, they have a hollow lumen and a thick cell wall strengthened by rings of lignen.
What are xylem vessels lignified to do?
withstand pressure changes as water moves through the plant
How is sugar transported up and down the plant?
living phloem
What is the structure of phloem tissue
phloem is a living tissue and it is composed of two main cell types, sieve tube cells and companion cells
What do phloem cells have?
sieve plates and associated companion cells
Describe the pathway that oxygenated and deoxygenated blood take through the heart, lungs and the rest of the body.
Blood that has circulated around the body is deoxygenated. This means that it is low in oxygen, and high in carbon dioxide and haemoglobin in the red blood cells. This blood enters the heart through a large vein, the vena cava. The blood then enters the first heart chamber, the right atrium. As the atrium contracts, blood flows from the right atrium into the right ventricle.
When the right ventricle contracts, the blood then leaves the heart through the pulmonary artery and goes to the lungs. In the lungs the carbon dioxide is lost as waste and the haemoglobin in the red blood cells is converted to oxyhaemoglobin. The blood is now oxygenated.
The oxygenated blood then returns to the heart through the pulmonary vein. The blood enters the left atrium of the heart. When the left atrium contracts the blood flows from the left atrium into the left ventricle.
The left ventricle then contracts and blood leaves the heart through the aorta to go to the rest of the body. The aorta branches into other arteries, which then branch into smaller arterioles. The arterioles join with capillaries, which is where gas exchange occurs. The first branch of the aorta is the coronary artery. This takes blood to the heart muscle itself. The blood is then returned to the heart in veins.
What is the function of the right atria?
The right atria collects deoxygenated blood from the vena cava and passes it to the right ventricle.
What is the function of the left atria?
The left atria collects oxygenated blood from the pulmonary vein and passes it to the left ventricle.
What is the function of the right ventricle?
The right ventricle collects deoxygenated blood from the right atria and pumps it through the aorta.
What is the function of the left ventricle?
The left ventricle collects oxygenated blood from the left atria and pumps it through the aorta.
What do the two heart valves do that are found between the atria and ventricles?
They prevent backflow from the ventricles to the atria.
Where are the heart valves found?
Two are found between the atria and ventricles, on each side of the heart. Two are found at the exits of the ventricles, one on each side of the heart.
What do the two heart valves do that are at the exits of the ventricles?
they prevent backflow of blood from the arteries into the ventricles.
What is the function of the aorta?
The aorta accepts oxygenated blood pumped at high pressure by the left ventricle and distributes it to the body.
What is the function of the vena cava?
The vena cava collects deoxygenated blood oozing at low pressure from the lungs and passes this blood to the left atria.
What is the function of the pulmonary vein?
Collects oxygenated blood oozing at low pressure from the lungs and passes this blood to the left atria.
What is the function of the pulmonary artery?
accepts deoxygenated blood pumped at high pressure by the right ventricle and distributes it to the lungs.
What is the function of the coronary artery?
accepts oxygenated blood pumped at high pressure by the left ventricle and distributes it to the heart muscle itself
Describe the structure and function of arteries
They have thick muscular walls, a narrow central channel and carry blood under high pressure away from the heart
Describe the structure and function of veins
Veins have thinner walls, a wider channel and carry blood under low pressure back towards the heart
Why do veins contain valves?
to stop the backflow of blood
Where do capillaries form networks?
at organs and tissues
Describe the features of capillaries that allow efficient exchange of materials
the walls of capillaries are only one cell thick. This makes the exchange surface very thin, shortening the diffusion distance across which gases have to move. They are also in very close contact with body tissue, decreasing the diffusion distance. Capillaries are numerous in number; this presents a large surface area for gas exchange to occur.
What are lungs?
gas exchange organs
What do lungs consist of?
A large number of alveoli providing a large surface area
What are oxygen and carbon dioxide absorbed through?
the thin alveolar walls to or from the many blood vessels
Where are nutrients from the food absorbed into?
the villi in the small intenstine
What do the large number of villi provide?
a large surface area
What does each villus contain?
a network of capillaries to absorb glucose and amino acids and a lacteal to absorb fatty acids
What is a tissue?
a group of similar cells that carry out the same function.
