Identify the cell, organelle or developmental process first, then use scale, structure, chromosome or expression evidence to justify the biological conclusion.
The photograph shows two human cheek cells on a microscope slide. The mean diameter of human cheek cells is .
(Source: © BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY)
Describe a procedure for the accurate determination of the diameter of cell A .
Draw cell A and label the parts of the cell.
Include a scale by your drawing.
The photograph below shows part of a transverse section of a plant stem.
Three types of cell are labelled X, Y and Z.
(Source: DR KEITH WHEELER / SCIENCE PHOTO LIBRARY)
Identify the cell types labelled X, Y and Z.
X
Y
Z
The photograph shows a longitudinal section of where two plant cells meet.
(Source: DR KEITH WHEELER / SCIENCE PHOTO LIBRARY)
State which of the cells labelled X, Y or Z is shown in this longitudinal section.
Cell
The five stages of cancer are used to describe the size and spread of a cancer in a human body.
The mitotic index of a tissue can be used to determine the stage of cancer.
A higher mitotic index is usually linked to a later stage of cancer.
The mitotic index is calculated using the formula
Tests were performed on three patients, P, Q and R, who had cancer.
The table shows the number of cells that were counted in each stage of the cell cycle per of tissue, taken from the same organ in each patient.
State what is meant by the term tissue.
A student used a microscope to study the tissues in a plant stem and the cell of an animal.
The photograph shows a vascular bundle in a transverse section of the plant stem, as seen using a light microscope.
The photograph shows an animal cell. This photograph was taken using an electron microscope.
Draw this cell as the student would see it under high power of a light microscope.
Label your diagram to show the nucleus, the nucleolus and the nuclear envelope.
State one difference and one similarity between the nuclear envelope and the cell membrane.
Difference
Similarity
A student used a microscope to study the tissues in a plant stem and the cell of an animal.
The photograph shows a vascular bundle in a transverse section of the plant stem, as seen using a light microscope.
State one difference and one similarity between the nuclear envelope and the cell membrane.
Difference
Similarity
Insulin is a protein produced in beta cells in the pancreas.
Ribosomes are involved in the production of insulin.
Describe how the protein insulin is transported from the ribosomes and then secreted by a beta cell.
All organisms contain one or more cells.
In which of the following is a cell wall present?
plant cells only
animal and plant cells only
plant and prokaryotic cells only
animal, plant and prokaryotic cells
Sailor's eyeball (Valonia ventricosa) is a single-celled, spherical organism. The diagram shows one of these cells.
This cell is not a prokaryotic cell as it contains chloroplasts.
Give one other reason why this organism is not a prokaryotic cell.
Insulin is a protein produced in beta cells in the pancreas.
Ribosomes are involved in the production of insulin.
The photographs show part of a beta cell from the pancreas, as seen using an electron microscope.
(Source: © Don Fawcett/Science Photo Library
© Martin M. Rotker/Science Photo Library)
The structures labelled T and U are the same type of organelle.
Suggest why these structures look different in this photograph.
Abaca plants are found in the Philippines.
The photograph shows a mat made from abaca plant fibres.
Plant fibres include xylem vessels.
The photograph shows some xylem vessels, as seen using a light microscope.
A stain was added to the xylem before viewing using a microscope.
Give a reason why it is usual to stain specimens in microscopy.
A student used a microscope to study the tissues in a plant stem and the cell of an animal.
The photograph shows a vascular bundle in a transverse section of the plant stem, as seen using a light microscope.
The photograph shows an animal cell. This photograph was taken using an electron microscope.
Draw this cell as the student would see it under high power of a light microscope.
Label your diagram to show the nucleus, the nucleolus and the nuclear envelope.
The photograph shows some pollen grains, as seen using an electron microscope.
Flower colour and pollen grain size are genetically determined in foxglove plants. The linkage of the genes for flower colour and pollen grain size has been investigated.
State what is meant by the term linkage with reference to these two genes.
The photograph shows a mother and baby Malayan tapir (Tapirus indicus). They live in the rainforests of southeast Asia. Each gamete of a Malayan tapir contains 26 chromosomes.
© Sipa US / Alamy Stock Photo
The body cells of the mother Malayan tapir have some genetic similarities to and differences from the cells of her baby. Explain why the body cells of the mother and baby have genetic similarities and differences.
All living organisms are made of cells. Some cells are specialised for their function.
One specialised cell is the sperm cell. Draw a mammalian sperm cell showing the acrosome, the nucleus and a mitochondrion. Label the acrosome, nucleus and mitochondrion.
A human egg cell is another example of a specialised cell.
Explain three ways in which a mammalian egg cell is specialised for its functions.
Fertilisation in mammals, such as the African northern white rhino, results in the fusion of gamete nuclei.
The photograph shows the last two remaining northern white rhinos.
Both of these rhinos are female.
Sperm and tissue samples were taken from the last few male northern white rhinos before they died. The sperm samples were frozen.
Sperm cells contain a digestive enzyme called acrosin.
The effect of acrosin activity of samples of sperm cells on the percentage of egg cells fertilised was investigated.
The graph shows the results of this investigation.
> acrosin activity of the sperm cell/a.u. sample
Explain why a higher activity of the digestive enzyme acrosin resulted in a higher percentage of egg cells being fertilised.
In vitro fertilisation (IVF) has been used to fertilise northern white rhino egg cells using the frozen sperm samples.
The zona pellucida of some egg cells were damaged when they were removed from the ovaries of the females.
The drawing shows a fertilised egg cell with three nuclei.
magnification \(\times 200\)
Suggest why this fertilised egg cell has three nuclei.
The photograph shows some pollen grains, as seen using an electron microscope.
A pollen grain can produce a pollen tube that contains a generative nucleus.
Plant fertilisation results in the production of an embryo and endosperm tissue. The diagram shows the location of an embryo and endosperm tissue in a seed.
Describe how the generative nucleus results in the production of an embryo and endosperm tissue in a seed.
Mitosis can occur in some plant cells.
The photograph shows a plant cell as seen using a light microscope.
Name the stage of mitosis shown in this photograph.
Describe what happens during the telophase stage of mitosis in a plant cell.
The flow chart shows how garlic root tips can be treated to observe mitosis in the root cells.
Give one reason why each of the following steps was taken.
(3)
Step 2
Step 4
Step 5
Describe how the procedure shown in the flow chart could be used to investigate the effect of pH on the mitotic index.
Flowering plants produce seeds that can be stored in a seed bank. This is done to conserve the biodiversity of plants.
The longer seeds are stored in seed banks, the less likely they are to germinate. This is due to ageing.
Ageing of seeds can affect the growth of roots when the seeds germinate.
Determining the mitotic index of roots is one way to study growth of roots.
Describe how the mitotic index of roots can be determined.
Seeds can be treated to artificially age them.
In an investigation, untreated and treated samples of seeds were germinated and the roots allowed to grow.
Roots of different lengths from the untreated seeds, seeds treated for 4 days and seeds treated for 14 days were selected.
The mitotic index of these roots was determined.
The graph shows the results of this investigation.
There were 14 cells undergoing mitosis in 8 mm roots from seeds treated for 4 days. Calculate the total number of cells that were counted when the mitotic index was determined.
(3)
Total cells counted
All living organisms are made of cells. Some cells are specialised for their function.
A fertilised egg cell develops into a morula and then a blastocyst.
Which of the following are correct statements?
1. A blastocyst contains pluripotent stem cells.
2. A blastocyst is a hollow ball of cells whereas a morula is not.
3. Both of these structures contain cells which divide by meiosis.
□ A 1 and 2 only
□ B 1 and 3 only
□ C 2 and 3 only
□ D 1, 2 and 3
Insulin is a protein produced in beta cells in the pancreas.
Ribosomes are involved in the production of insulin.
Explain why beta cells can produce insulin but other cells in the pancreas do not.
Multicellular organisms, like starfish, contain many different types of cells.
One gene from this starfish pluripotent stem cell produces pre-mRNA. The diagram shows how three different strands of active mRNA are produced from one strand of pre-mRNA.
Explain how these three active mRNA strands are produced. Use the diagram to support your answer.
Proteins can control cell processes and determine cell structure.
DNA methylation can alter the activation of a gene.
Suggest the role of the enzyme DNA methyltransferase (DNMT) in the process of DNA methylation.
Some cancers can be caused by the methylation of a tumour suppressor gene called RASSF1. Tumour suppressor genes can slow down cell division or cause cell death. Peperomin E is a drug that can cause the demethylation of the gene RASSF1. In an investigation different treatments were given to groups of 10 mice. These mice had identical lung cancer tumours at the start of the investigation. Graph A shows the changes in tumour volume for each group, over 21 days. Relative volume of tumour Thero Group A no treatment
Graph A Graph B shows the mean mass of tumours at 21 days.
Graph B
Explain how treatment with these two drugs affects the activity of the RASSF1 gene and the changes in tumours. Use all of the information in part (c) and your own knowledge to support your answer.
The common wombat is endemic to Australia and Tasmania.
The photograph shows a common wombat.
magnification
The height of a wombat is a result of polygenic inheritance.
State what is meant by the term polygenic inheritance with reference to wombat height.