IGCSE Biology Characteristics & classification topical questions

Name the characteristic of living organisms described by each sentence.

1. (a)The chemical reactions in cells that break down nutrient molecules and release energy.[1]
2. (b)The taking in of materials for energy, growth and development.[1]
3. (c)The ability to detect and respond to changes in the environment.[1]

A seal lives on a rocky shore. It catches fish, dives to escape storms, and returns to the same beach each year to breed.

1. (a)Name the characteristic shown when the seal catches and eats fish.[1]
2. (b)Name the characteristic shown when the seal returns to breed.[1]
3. (c)The seal passes out a white waste solution from its body. Explain why this is excretion and not egestion.[2]

The scientific name of the sweet pea plant is Lathyrus odoratus.

1. (a)State how many name parts the binomial system gives every species.[1]
2. (b)Identify the genus of the sweet pea.[1]
3. (c)State one reason biologists use scientific names instead of common names.[1]
4. (d)A pea and a sweet pea can interbreed to produce fertile offspring. State what this shows about their classification.[1]

Four organisms are observed under a microscope and with a hand lens. Their features are listed in the table.

1. (a)Name the kingdom that each organism belongs to.[4]
2. (b)State one feature, visible in the table, that the bread mould and the fern share.[1]

Four vertebrates are described: P is covered in feathers and lays hard-shelled eggs; Q has moist skin and its tadpole larvae live in water; R has dry scaly skin and lays leathery eggs on land; S has fur and its young drink milk.

1. (a)Identify the vertebrate class of each animal, P to S.[4]
2. (b)State one feature, other than those given, that confirms animal S is a mammal.[1]

A student collects four arthropods and records their features in a table.

1. (a)Identify the arthropod group of each animal, W to Z.[4]
2. (b)State one feature, visible in the table, that all four arthropods share.[1]
3. (c)Name the group the animals all belong to.[1]

Using the data in the table from Question 5, construct a dichotomous key that identifies W, X, Y and Z.

1. (a)Write out your key in numbered steps, each with two contrasting statements.[3]
2. (b)Explain why "has wings / has no wings" would be a poor first split for this key.[1]

A student scoops four small animals out of a pond and records their features in a table.

1. (a)Construct a dichotomous key that identifies all four animals, using only the features in the table.[4]
2. (b)The water louse and the freshwater shrimp are both crustaceans. State the feature in the table that shows neither is an insect.[1]
3. (c)The pond snail is an animal but not an arthropod. Use the table to explain why.[1]

The sequence of one gene is compared between four cat species. The numbers of bases that differ are shown in the table.

1. (a)Identify the two species that share the most recent common ancestor.[1]
2. (b)Explain how these data support the idea that classification should reflect evolutionary relationships.[3]
3. (c)These four cats were once placed in different genera because of differences in appearance, such as mane colour and spot pattern. Suggest one advantage of reclassifying them using DNA base sequences.[2]
4. (d)Lions and tigers can interbreed in captivity, but their hybrid offspring are sterile. Explain why they remain separate species.[1]

Five organisms are described. A is multicellular with no cell walls and engulfs its food; B is multicellular with cellulose cell walls and chloroplasts; C is unicellular with a nucleus and no chloroplasts, feeding on dead leaves; D is unicellular with circular DNA but no nucleus; E is unicellular with a nucleus and a red light-sensitive spot, and makes its own sugars.

1. (a)Place each organism into one of the five kingdoms.[5]
2. (b)State the feature that places D in its kingdom rather than with E.[1]

The base sequence of the same gene is compared between four species. The numbers of bases that differ are: badger–otter 4; badger–weasel 4; otter–weasel 21; weasel–mink 6; badger–mink 25.

1. (a)Explain why DNA base sequences can be used to classify organisms.[2]
2. (b)Identify the two species in this data set that share the most recent common ancestor, giving a reason.[2]
3. (c)Scientists once classified these species by appearance alone. Suggest one advantage of using DNA sequences as well.[2]
4. (d)State the term that describes the group each of these species belongs to: they are all animals with backbones.[1]

A microbiologist discovers three new organisms and records the following. Organism P: unicellular, with a nucleus, chloroplasts and a cell wall not made of cellulose; lives in fresh water. Organism Q: multicellular, cell walls of chitin, no chloroplasts, absorbs nutrients from dead leaves. Organism R: a particle with a protein coat and RNA inside, which reproduces only inside bacterial cells.

1. (a)Name the kingdom of organism P and give two features from the description that support your answer.[3]
2. (b)A student places organism Q in the plant kingdom. Explain why this is incorrect and name the correct kingdom.[2]
3. (c)Explain why organism R is not placed in any kingdom.[2]

A student writes a dichotomous key for four pond animals: W has a shell and no legs; X has three pairs of legs; Y has seven pairs of legs and one pair of antennae; Z has eight pairs of legs and no antennae. The student’s key reads: 1 (a) has a shell → go to 2; (b) has no shell → go to 2. 2 (a) has legs → go to 3; (b) has no legs → W. 3 (a) one pair of antennae → X; (b) no antennae → Y.

1. (a)Identify two faults in the student’s key.[2]
2. (b)Write a corrected dichotomous key that identifies all four animals.[3]
3. (c)State one feature of a well-designed dichotomous key.[1]

Two populations of a small bird look almost identical: population P lives on an island, population Q on the nearby mainland. Zookeepers find that birds from P and Q interbreed and the offspring are fertile. The DNA of the same gene from both populations differs by only 2 bases.

1. (a)Use the evidence to state whether the two populations belong to the same species. Give a reason.[2]
2. (b)Explain how the DNA evidence shows that P and Q share a recent common ancestor.[2]
3. (c)Suggest why classification systems may change when new evidence, such as DNA sequences, becomes available.[2]