24 reviewed questions with answers and explanations.
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An Amoeba and an unfertilised chicken ovum are each
C: a single cell
Amoeba is a unicellular organism, while an unfertilised chicken ovum is a single reproductive cell. The ovum is not the whole shelled egg with its surrounding membranes and albumen.
AI-reviewed · source checkedThe organisms that move by means of flagella include
A: Chlamydomonas and Euglena
Chlamydomonas and Euglena can swim using flagella. Amoeba moves by pseudopodia, and Paramecium uses many cilia rather than the flagellar swimming pattern of the first pair.
AI-reviewed · source checkedWhich pair occurs in photosynthetic plant cells but is absent from animal cells?
C: cell wall and chloroplast
Photosynthetic plant cells can have a cellulose wall and chloroplasts, whereas animal cells lack both. Cell membranes, cytoplasm, chromatin and nucleoli are shared eukaryotic features.
AI-reviewed · source checkedOne of the adaptations to life on trees by a monkey is its possession of digits which are
C: opposable
Opposable digits can close against other digits, improving the grip on branches. This is useful for climbing and holding supports during movement through trees.
AI-reviewed · source checkedPlants tend to prevent overcrowding by means of efficient
D: seed dispersal
Seed dispersal carries offspring away from the parent and from one another. This can reduce local competition for light, water, nutrients and space.
AI-reviewed · source checkedA field sample records 48 waterleaf plants in 20 placements of a 2 m² quadrat. What is the estimated plant density?
A: 1.2 per m²
The sampled area is 20 × 2 = 40 m². Dividing the total count, 48 plants, by 40 m² gives an estimated density of 1.2 plants per square metre.
AI-reviewed · calculation checkedSupporting xylem tissue is typically least developed in
C: submerged water plants
Submerged plants receive mechanical support from the surrounding water and can absorb water across much of their surface. Their supporting and conducting xylem is often reduced compared with terrestrial plants.
AI-reviewed · source checkedWith comparable representative sampling effort, which habitat would generally be expected to yield the highest species richness?
A: a tropical rain forest
Tropical rain forests generally support high species richness because of their complex structure and diverse ecological opportunities. Comparable representative sampling commonly finds more species there than in the other listed regional habitats.
AI-reviewed · source checkedIn his theory of evolution, Darwin implied that
B: the most successful organisms are those best adapted to their environment
Natural selection favours inherited variants that improve reproductive success in the current environment. Individuals carrying favourable variants tend to leave more descendants, changing their frequency over generations.
AI-reviewed · source checkedBirds which are large with long straight pointed beaks, long necks and long legs are likely to be
B: fish catchers
Long legs and necks allow a wading bird to reach into water, and a long pointed bill can seize aquatic prey. These features are consistent with a fish-catching bird such as a heron.
AI-reviewed · source checkedExamples of organisms in which extracellular digestion occurs are
D: Rhizopus, housefly and Hydra
Rhizopus releases digestive enzymes outside its cells. A housefly digests food externally or in its gut, and Hydra begins digestion in its gastrovascular cavity. All therefore have extracellular digestion.
AI-reviewed · source checkedTypical mature mammalian erythrocytes are
B: discoid and enucleated
Typical mature mammalian red blood cells are disc-shaped and lack a nucleus. Losing the nucleus helps provide space for haemoglobin, although shape varies in some mammalian groups.
AI-reviewed · source checkedA characteristic internal skeleton of cartilage or bone is associated with
B: vertebrata
Vertebrates characteristically have an internal skeleton of cartilage or bone. This endoskeleton supports the body and provides attachment points for muscles.
AI-reviewed · source checkedThe capture and digestion of insects by a pitcher plant is a special form of nutrition termed
B: heterotrophic
Capturing and digesting insects supplies nutrients from other organisms, a heterotrophic supplement to the pitcher plant’s photosynthesis. The plant can still obtain much of its carbon by photosynthesis.
AI-reviewed · source checkedOne leaf of a living plant is enclosed through a stopper in a flask containing caustic soda below the leaf; other leaves remain outside. The flask is supported on a retort stand. Which statement correctly describes the intended comparison?
D: The leaves outside the flask serve as control
The outside leaves provide a comparison with leaves exposed to ordinary air. Caustic soda removes carbon dioxide inside the flask, so the enclosed leaf has a different carbon dioxide supply.
AI-reviewed · source checkedOne leaf of a living plant is enclosed through a stopper in a flask containing caustic soda below the leaf; other leaves remain outside. The flask is supported on a retort stand. Which requirement is this setup intended to investigate?
D: carbon (IV) oxide is necessary for photosynthesis
Caustic soda absorbs carbon dioxide, changing the supply available to the enclosed leaf. The setup is intended to test the need for CO2 in photosynthesis; meaningful starch comparisons also require appropriate prior preparation and matched conditions.
AI-reviewed · source checkedWhich pair of organs occupies the thoracic cavity of a mammal?
C: lungs and heart
The heart and lungs occupy the thoracic cavity, anterior to the main abdominal organs in a typical quadruped. The kidneys and ovaries lie farther back in the abdominal region.
AI-reviewed · source checkedThe most specific description of a tapeworm’s nutritional relationship with its living host is
C: parasitic
A tapeworm obtains nutrients from a living host and can harm it. This is parasitism. Its body surface absorbs nutrients already digested in the host’s intestine.
AI-reviewed · source checkedThe head of which organ lies within the duodenal loop in a mammal?
B: pancreas
The head of the pancreas lies within the curve of the duodenum. Pancreatic secretions reach the small intestine through ducts and assist digestion.
AI-reviewed · source checkedIn which of the following groups of fruits is the pericarp inseparable from the seed coat?
D: Caryopsis
A caryopsis is a dry, one-seeded fruit in which the fruit wall is closely fused with the seed coat. Cereal grains such as maize are examples.
AI-reviewed · source checkedTissue respiration is important for the
C: release of energy for body use
Cellular respiration transfers energy from food molecules into forms cells can use, especially ATP. Breathing and gas exchange supply or remove gases but are different processes.
AI-reviewed · source checkedIn a model of X-linked red–green colour-vision deficiency, Xᴺ is the dominant normal allele and Xⁿ the recessive allele. A boy with genotype XⁿY will
B: have red–green colour-vision deficiency
In the stated X-linked recessive model, the boy has only the Xⁿ allele at this locus because the Y chromosome lacks a corresponding dominant allele. The colour-vision deficiency is therefore expressed.
AI-reviewed · source checkedAssume independent births with equal probabilities of a boy and a girl. A couple’s first four children were girls. What is the probability that the fifth will also be a girl?
D: ½
With independent births and a probability of one half for a girl in this model, the previous four outcomes do not change the fifth. The probability remains 1/2.
AI-reviewed · calculation checkedAt a single locus with complete dominance, what proportion of offspring from two heterozygous parents, Aa × Aa, is expected to express the recessive phenotype?
A: ¼
For Aa × Aa, the equally likely allele combinations are AA, Aa, aA and aa. With complete dominance, only aa expresses the recessive phenotype, giving a probability of 1/4.
AI-reviewed · calculation checked