48 questions. Try each one, then open the answer to check yourself and read the explanation.
In the egg of a bird, the embryo is located in the
Answer: D (embryo disc.)
The embryo grows from the small embryo (germinal) disc that sits on the surface of the yolk. The yolk and albumen feed it, and the chalazae hold the yolk in place.
One distinctive feature in the life history of liverworts is that they exhibit
Answer: A (Alternation of generation)
Liverworts alternate between a gametophyte generation (the green plant) and a sporophyte generation that grows on it. This alternation of generations is typical of bryophytes.
Use the diagram to answer: A noticeable adaptation of the animal to its aquatic habitat is the possession of
Answer: C (webbed digits)
The frog's toes are joined by skin (webbed). Webbed feet act like paddles for swimming.
Use the diagram to answer: The processes of water loss and intake indicated by the arrows labelled I and II are respectively.
Answer: D (evaporation and osmosis.)
Arrow I shows water leaving the moist skin into the air, which is evaporation. Arrow II shows water entering through the skin from the pond by osmosis, because the frog's body fluids are more concentrated than fresh water.
The umbrella-shaped fruiting body of a fully developed mushroom is the
Answer: A (Pileus)
The cap of a mushroom is called the pileus, and it sits on a stalk called the stipe. The gills under the cap carry basidia that make spores.
The similarity among organisms belonging to the same group will be least within each
Answer: C (kingdom)
The kingdom is the largest and widest group, so its members have the fewest features in common. Members of a species are the most alike.
Hermaphroditic reproduction can be found among the
Answer: C (Annelids and molluscs)
Earthworms (annelids) and land snails (molluscs) are the standard examples of hermaphrodites: each animal has both male and female organs.
An insect whose economic importance is both harmful and beneficial is the
Answer: D (Butterfly.)
Butterfly caterpillars eat crop leaves (harmful), but the adults pollinate flowers (beneficial). The tsetse fly, blackfly and mosquito are mainly harmful disease carriers.
The cell component that is present in a prokaryotic cell is the
Answer: B (Ribosome)
Prokaryotes such as bacteria have no membrane-bound organelles or nuclear envelope. They do have ribosomes for making proteins.
The stunted growth of a leguminous plant suffering from nitrogen deficiency may be corrected by inoculating the soil with
Answer: C (Rhizobium)
Rhizobium lives in the root nodules of legumes and fixes nitrogen from the air for the plant. Adding it to the soil helps a nitrogen-starved legume grow.
If water that has been coloured red is poured at the base of a wilting plant, it will appear as a red stain in the cells of the
Answer: A (xylem)
Water is carried up from the roots through the xylem. So the red dye shows up in the xylem vessels.
Use the diagram of the bell jar set-up to answer: The aim of the experiment is to demonstrate
Answer: B (the part played by the pleural cavity and diaphragm in respiration)
Pulling the rubber sheet down makes the space in the jar bigger, so the balloons fill with air; pushing it up deflates them. This models how the diaphragm and chest cavity work in breathing.
Use the diagram of the bell jar set-up to answer: In the experimental set-up, the rubber sheet represents the organ called
Answer: C (diaphragm)
The rubber sheet closes the bottom of the jar the way the diaphragm closes the bottom of the chest. Moving it up and down changes the volume inside.
The dark reaction of photosynthesis involves the
Answer: A (reduction of carbon (IV) oxide to organic compounds.)
In the dark (light-independent) stage, hydrogen from the light stage reduces carbon(IV) oxide to sugars. Splitting water and releasing oxygen happen in the light stage.
Use the diagram of the experiment to answer: The experiment is used to demonstrate that
Answer: B (transpiration occurs through the leaves)
Water drops collect on the inside of the bell jar with the leafy shoot but not with the leafless one. This shows that plants lose water vapour mainly through their leaves.
Use the diagram of the experiment to answer: In the experiment, the layer of oil serves to prevent water loss by
Answer: B (evaporation)
The oil covers the water in the beaker so none of it can evaporate. Any droplets in the jar must then come from the plant.
Organisms I, II, III and IV have surface/volume ratios of 1:2, 1:3, 1:4 and 1:5 respectively. The organism that is likely to have the most complex transport system is
Answer: A (IV)
The smaller the surface area compared with volume, the less an organism can rely on diffusion alone. IV has the smallest ratio (1:5), so it needs the most complex transport system.
The part of the mammalian digestive system where absorption of nutrients takes place is the
Answer: A (ileum)
The ileum is long and lined with villi that give a huge surface area. Most digested food is absorbed there.
The best method of propagating sugarcane is by
Answer: D (Stem cuttings.)
Sugarcane is grown from pieces of stem that have nodes and buds. Each cutting sprouts into a new plant.
In mammalian males, the excretory and reproductive systems share the
Answer: C (Urethra)
In males the urethra carries urine from the bladder and also carries semen. It is shared by both systems.
Metabolic production of urea is carried out in the
Answer: B (Liver)
The liver breaks down excess amino acids (deamination) and turns the ammonia into urea. The kidneys then filter the urea out of the blood.
Use the diagram of the neurone to answer: The structure can be found in the
Answer: B (Peripheral and central nervous systems)
Neurones like this are found in both the brain and spinal cord (central nervous system) and in the nerves of the body (peripheral nervous system).
Use the diagram of the neurone to answer: The point marked I is referred to as
Answer: D (node of Ranvier.)
Point I is the gap between two sections of the myelin sheath along the axon. These gaps are nodes of Ranvier, where the impulse jumps from node to node.
Homologous pairs of chromosomes separate during
Answer: D (Meiosis.)
In the first division of meiosis, homologous chromosomes pair up and then move to opposite poles. This halves the chromosome number for gametes.
An example of a caryopsis is
Answer: B (Maize grain)
A maize grain is a caryopsis: a dry one-seeded fruit whose wall is fused to the seed coat.
The response of plants to external stimuli in a non-directional manner is known as
Answer: D (Nastic movement.)
Nastic movements do not depend on the direction of the stimulus, such as the folding of Mimosa leaves when touched. Tropisms are directional growth responses.
The most important hormone that induces the ripening of fruit is
Answer: A (Ethylene)
Ethylene is a gas given off by ripening fruits. It speeds up ripening, which is why one ripe fruit can ripen others nearby.
A density-dependent factor that regulates the population size of organisms is
Answer: A (Disease)
Disease spreads more easily when organisms are crowded together, so its effect grows with population density. Floods, droughts and fires strike whatever the population size.
One example of fossil fuels is
Answer: C (Coal)
Coal formed over millions of years from buried plant remains, so it is a fossil fuel. Firewood is a renewable fuel from living trees.
The most effective method of dealing with non-biodegradable pollutants is by
Answer: B (Recycling)
Non-biodegradable waste such as plastic and metal does not rot. Recycling turns it into new products instead of leaving it in the environment.
The correct sequence of biomes from northern to southern Nigeria is
Answer: D (Sahel savanna → sudan savanna → guinea savanna → tropical rainforest → estuarine.)
Rainfall increases from north to south. So the order is Sahel savanna, Sudan savanna, Guinea savanna, rain forest, and finally the estuarine (mangrove) swamps at the coast.
Mycorrhiza is an association between fungi and
Answer: B (Roots of higher plants)
Mycorrhiza is a fungus living on or in plant roots. The fungus helps the root absorb minerals and gets sugars in return.
A limiting factor in a plant population near a chemical factory is likely to be
Answer: D (pH.)
Chemical factories release acidic gases and waste that change the acidity (pH) of the soil and water. This limits which plants can grow there.
Soil fertility can best be conserved and renewed by the activities of
Answer: D (Microbes.)
Bacteria and fungi decompose dead matter and release minerals back into the soil, and some fix nitrogen. This recycling keeps the soil fertile.
The pioneer organisms in ecological succession are usually the
Answer: B (lichens)
Lichens can grow on bare rock. They break it down slowly and start forming soil, so other plants can follow.
If a DNA strand has a base sequence TCA, its complementary strand must be
Answer: D (AGT.)
In DNA, A pairs with T and C pairs with G. So T-C-A pairs with A-G-T.
A man and his wife are both heterozygous for the sickle-cell trait. The likely percentage of their offspring that will be either carriers or 'sicklers' is
Answer: A (75%)
AS × AS gives AA, AS, AS and SS. Carriers (AS) and sicklers (SS) make 3 out of 4, which is 75%.
If the pair of alleles for baldness is given as Bb, a female carrier will be denoted by
Answer: D (XBXb.)
A female has two X chromosomes. A carrier has one normal (B) and one recessive (b) allele: XBXb.
An organism that has been extensively used to test the chromosome theory of heredity is
Answer: A (Drosophila melanogaster)
The fruit fly Drosophila breeds quickly, has few chromosomes and shows clear traits. T. H. Morgan used it to show that genes are carried on chromosomes.
A feature associated with the Y-chromosome in humans is
Answer: C (facial hairs)
The Y chromosome makes a baby develop as a male. Male features such as facial hair follow from it.
The type of reproduction that leads to variation in animal and plant populations is
Answer: B (sexual)
Sexual reproduction mixes genes from two parents, so the offspring differ from each other and from their parents. Asexual methods produce copies.
An insect with a mandibulate mouth part will obtain its food by
Answer: A (biting and chewing)
Mandibles are strong jaws for biting and chewing solid food, as in cockroaches and grasshoppers.
An argument against Lamarck's theory of evolution is that
Answer: C (acquired traits cannot be passed on to the offspring.)
Lamarck said features gained during life are inherited. But changes to body cells, such as big muscles, do not change the genes in the gametes, so they are not passed on.
The presence of sunken stomata and the folding of leaves are adaptations to
Answer: B (Reduce water loss)
Sunken stomata and rolled leaves trap moist air around the stomata. This slows transpiration, which helps plants in dry places.
Spines and shells on animals are adaptations for
Answer: C (physical defence)
Spines (as on a porcupine) and shells (as on a snail or tortoise) physically block or hurt attackers. This is physical defence.
An example of cryptic colouration is the
Answer: A (Mottled colours on moths that rest on lichens)
Cryptic colouration helps an animal blend into its background. A mottled moth resting on lichens is hard to see, while a poisonous frog's bright marks are a warning.
Which of the following requires the use of carbon dating to prove that evolution has occurred?
Answer: D (Fossil records)
Radioactive (carbon) dating tells how old fossils and rocks are. This lets scientists put fossils in time order and see how organisms changed.
The inactive state exhibited by an animal during hot dry seasons is termed
Answer: A (Aestivation)
Aestivation is a resting state during hot, dry seasons. Hibernation is the same kind of rest during cold seasons.