biology multicellular organisms Flashcards
sequence of events of mitosis
- chromosomes become visible as pairs of chromatids
2.chromatic cells line up on the equator of the cell - pairs of chromatids attach to the spindle fibres near the middle of the cell
- spindle fibres pull chromatids apart
- daughter chromosomes gather at the ends of the cell
- the cytoplasm divides forming two diploid cells.
describe diploid cell
A diploid cell had two matching sets of chromosomes.
Most cells (the exception being the gametes) in the human body are diploid. They contain 2 sets of 23 chromosomes, giving a total of 46 chromosomes.
Both sets are replicated during mitosis.
importance of mitosis
Mitosis maintains the diploid chromosome complement of the new cells, providing the body with new cells that can be used in growth and repair.
describe a stem cell and how they are used in animals
A stem cell in an animal is an unspecialised cell that can divide to self-renew (produce more stem cells) or become specialised. They have the potential to become any cell type in the body.
Stem cells are used in growth and repair.
State where stem cells are found
There are 2 types of stem cell:
Embryonic stem cells are taken from an embryo at a very early stage.
Tissue stem cells are found in the body throughout life.
Explain the importance of the specialisation of cells
Cells become specialised to give rise to a variety of cells, each with a particular function.
Describe the role of an organ, explaining the terms tissue, organ and organ system
A tissue is a group of cells.
An organ is a group of tissues.
An organ system is a group of organs.
An organ contains cells specialised for a particular function and groups of organs work together to form systems.
State the hierarchy of organ systems
Cells → Tissues → Organs → Organ systems
Describe 2 responses to a stimulus
A response can be a rapid action from a muscle, or a slower response from a gland by the release of a chemical.
Describe the components of the nervous system including the CNS
The nervous system is made up of the central nervous system (CNS) and other nerves.
The CNS consists of the spinal cord and the brain.
Describe the structure and function of the brain
Cerebrum - controls conscious thought and actions, memories and personality
Cerebellum - controls balance and movement
Medulla - controls heart rate and breathing rate
what does a sensory neuron do
Pass information from the senses to the CNS
what does an inter neuron do
Located in the CNS and processes information from the senses that require a response
what does a motor neuron do
enable a response to occur at an effector (a muscle or gland)
describe how neurons transmit messages
Sensory neurons contain receptors which detect stimuli (sensory changes) and send an electrical impulse to the inter neuron and then a motor neuron to bring about a response.
Describe a synapse
Neurons are connected by tiny gaps called Synapses.
Chemicals diffuse across the gap to carry the impulse from one neuron to another.
Describe the structure and function of the reflex arc
Rapid and protects the body from harm.
Describe a hormone
A hormone is a chemical messenger released into the bloodstream.
describe how target tissues recognise hormones
The target tissue contains special receptor proteins that will recognise the hormone.
The receptor proteins ensure only the target tissues are affected by the hormone.
Describe an endocrine gland using examples
Endocrine glands release hormones into the bloodstream.
The three main endocrine glands are:
The pancreas
The ovaries (females)
The testes (males)
Describe how the body responds to an increase in blood glucose
An increase in blood glucose leads to the following action.
The pancreas responds by releasing the hormone insulin.
Receptors in the liver detect the insulin.
In response, the liver starts to convert excess glucose into glycogen.
The blood glucose levels fall.
Describe how the body responds to a decrease in blood glucose
A decrease in blood glucose leads to the following action.
The pancreas responds by releasing the hormone glucagon.
Receptors in the liver detect the glucagon.
In response the liver starts to convert glycogen back into glucose.
The blood glucose levels rise.
When the glucose is gone, it is time for glucagon!
Define a gamete, locating where they are produced in animals
A gamete is a sex cell and is involved in reproduction.
Gametes are HAPLOID, meaning they contain only half of the genetic information of diploid cells.
In humans - an egg and sperm cell contain 23 chromosomes (1 set).
The female gametes are eggs and are produced in the ovaries.
The male gamete is sperm and is produced in the testes.
Describe and locate where gametes are produced in plants
The female gametes are eggs/ovules and are produced in the ovary.
The male gamete is pollen and is produced in the anther.
Describe the process of fertilisation
Fertilisation is when the nuclei of 2 haploid gametes fuse together to form a diploid zygote, which divides to form an embryo.
Define discrete variation
Discrete variation is caused by inheritance due to a single gene. Measurements of the characteristic fall into distinct groups.
e.g. blood groups
define continuous variation
Continuous variation is caused by polygenic inheritance (characteristics affected by more than one gene). Measurements of continuous variation occur over a range of values between a minimum and a maximum.
e.g. skin colour, leaf area, height.
what is a gene
a small section of DNA that codes for 1 protein which controls a particular characteristic.
what is an allele
different forms (versions) of the same gene. e.g. Gene = eye colour, Allele = Blue, brown, green etc.
what is a phenotype
Phenotype is a ‘physical’ description of a characteristic. e.g. Blue eyes, Brown eyes.
what is a genotype
description of the genes using letters to represent the alleles.
what is dominant
some alleles are dominant over other alleles. You only need to inherit one copy of a dominant allele to express the characteristic. Dominant alleles are always represented using capital letters.
what is recessive
These alleles are often masked by dominant alleles and you have to inherit 2 copies to express this characteristic. These alleles are represented by using lower case letters of the dominant characteristic.
what is homozygous
If you inherit 2 of the same alleles, you are homozygous for a characteristic.
what is heterozygous
If you inherit 2 different alleles i.e. 1 dominant and 1 recessive then you are said to be heterozygous for a particular characteristic.
State reasons why predicted phenotypic ratios are not achieved
Phenotypic ratios are not always achieved because fertilisation is a random process and the ratio is also dependent on the sample size.
If the sample size is too small, then the expected phenotypic ratio may not be shown.
Name the three main plant organs
The main plant organs are the leaves, roots and the stem.
Waxy Cuticle
Prevents water loss
Palisade mesophyll
Main cells involved in photosynthesis.
Upper epidermis
Allows light to pass through and prevents water loss.
Spongy mesophyll
Contain air spaces to allow gas exchange
Guard cells
control the opening and closing of stomata.
Stomata
Air spaces that allows oxygen and water to leave and carbon dioxide to enter the leaf.
Describe how a plant obtains water
A plant obtains water through the roots.
Roots contain specialised cells called root hair cells.
These cells increase the surface area in which the plant can absorb water and nutrients from the soil
Describe how the plant transports water and minerals
Water is transported from the roots to other parts of the plant through dead Xylem vessels.
These dead xylem vessels(lignified) contains rings of lignin. This allows the xylem vessel to withstand the pressure changes as water moves throughout the plant.
Describe the process of transpiration
Transpiration is the movement of water throughout the plant. Water evaporates from the stomata in the leaf, this causes pressure changes within the plant meaning more water is drawn through the plant from the roots back into the leaves.
Identify factors that affect transpiration
Wind speed
Humidity
Temperature
Surface area
Describe how sugar is transported around the plant
Sugar is transported up and down the plant in living phloem tissue.
Phloem cells have sieve plates and associated companion cells to allow sugar to be transported to all parts of the plant.
Describe the components of blood in mammals
Blood contains plasma, red blood cells and white blood cells. It transports nutrients, oxygen and carbon dioxide.
Describe how red blood cells are specialised to transport oxygen
Red blood cells are specialised cells, so they efficiently transport oxygen.
Red blood cells contain no nucleus
Red blood cells are biconcave in shape
Red blood cells contain the protein haemoglobin
word equation for haemoglobin and oxygen
It is haemoglobin that binds to oxygen. This process happens in the alveoli in the lungs, where the oxygen concentration is high.
Oxygen + Haemoglobin → Oxyhaemoglobin
This is a reversible reaction and oxygen will dissociate from haemoglobin in body tissues, where there is a low concentration of oxygen.
Oxygen + Haemoglobin ← Oxyhaemoglobin
describe the term pathogen
Pathogens are disease-causing micro-organisms (bacteria, viruses and fungi).
Name the two different types of white blood cells
Lymphocytes
Phagocytes
Describe the process of phagocytosis
Phagocytosis is the process by which phagocytes will engulf and digest the pathogen.
Phagocyte surrounds the pathogen
Phagocyte engulfs the pathogen and encloses it in a vacuole
Digestive enzymes within lysosomes in phagocytes digest the pathogen
Describe the role of antibodies when destroying a pathogen
Lymphocytes produce antibodies which will bind to a specific protein on the pathogen, called an antigen.
Antibodies will bind to several pathogens preventing the pathogen from spreading and allowing phagocytes to engulf the pathogen.
Antibodies are specific and only one antibody is specific to one pathogen.
the main structures within the heart
right artrium
left artrium
right ventricle
left ventricle
valves
vena cava
pulmonary artery
pulmonary vein
aorta
coronary arteries
describe the function of the artria
pump blood into the ventricles
describe the function of the ventricles
pump blood out of the heart
describe the function of the vena cava
brings deoxygenated blood from the body into the right atria
describe the function of the pulmonary artery
carries deoxygenated blood from the right ventricle to the lungs
describe the function of the pulmonary vein
carries oxygenated blood to the left atria from the lungs
describe the function of the aorta
carries oxygenated blood from the left ventricle to the rest of the body (except the lungs)
describe the function of the valves
prevents the backflow of blood into the heart
decribe the function of the coronary arteries
provide the heart muscle with oxygen, glucose and amino acids
Describe the pathway of oxygenated and deoxygenated blood through the heart
Deoxygenated blood enters the right side of the heart through the vena cava and enters the right atrium. It is pumped into the right ventricle and is pumped out of the heart through the pulmonary artery to the lungs.
Oxygenated blood returns from the lungs to the left side of the heart, it enters through the pulmonary vein into the left atrium. It is pumped out of the left atrium into the left ventricle and out of the left side of the heart to the rest of the body through the aorta.
Describe the structure and function of arteries
The Lumen of an artery is smaller than that of a vein and it has a thicker layer of smooth muscle to withstand the high pressure of blood. Arteries carry oxygenated blood from the heart to the body (1 exception).
Describe the structure and function of veins
Veins have a larger lumen, a smaller layer of smooth muscle and carries deoxygenated blood (1 exception) under lower pressure. Veins also contain valve.
Describe the structure and function of capillaries
Capillaries have a large surface area and form a dense capillary network. They are only 1 cell thick to allow fast exchange of substances between the blood and body tissues.
Describe blood and tissue functions
Oxygen and nutrients from food must be absorbed into the bloodstream to be delivered to cells for respiration.
Waste materials such as carbon dioxide, must be removed from cells into the bloodstream.
Tissues contain capillary networks that allow the exchange of materials to a cellular level.
Describe features of surfaces involved in the absorption of material
Surfaces involved in the absorption of materials have certain features in common:
Large surface area
Thin walls
Extensive blood supply
These increase the efficiency at which materials are absorbed.
describe the function of the lungs
The lungs are the gas exchange organs. They consist of a large number of alveoli providing a large surface area for gas exchange.
Oxygen into the blood is exchanged for carbon dioxide out of the blood.
Describe how oxygen and carbon dioxide are exchanged in the lungs
Oxygen and carbon dioxide are absorbed through the thin alveolar walls to or from the many blood capillaries.
Describe where nutrients are absorbed into the blood
Nutrients from food are absorbed into the blood in the small intestine.
The small intestine contains a large number of thin-walled villi to provide a large surface area for this absorption.
Describe the structure and function of the villi
The network of capillaries within the villi absorbs glucose and amino acids.
The lacteal absorbs fatty acids and glycerol.
