Textbook Solution: Classification | IGCSE Cambridge Science for Year 6 - Class 6 PDF Download

Classifying Organism

Q1. Describe three characteristics of tigers.

Ans: Tigers are known for their distinct orange coat with black stripes, powerful and muscular body, and their status as top predators in their ecosystems.

Q2. Describe the variations in two characteristics that tigers and humans share.

Ans: Both tigers and humans have hair, though it varies widely with tigers having a thick fur coat and humans having much less dense and shorter hair. Additionally, both species exhibit individual facial features, but tigers' facial markings are unique to each individual, aiding in their identification.

Q3. Which kingdom do these organisms belong to?

Ans: The organisms belong to the kingdom Animalia (options a, c, and e: cat, lion, and elephant).

Q4. State one characteristic that is the same in plants and animals.

Ans: Both plants and animals are made up of cells, which are the basic unit of life in both kingdoms.

Q5. Explain why fungi are in their own kingdom and not in the plant kingdom.

Ans: Fungi are placed in their own kingdom because they obtain nutrients through absorption rather than photosynthesis, have cell walls made of chitin (not cellulose), and reproduce via spores.

Q6a. How can you tell if a cell is a yeast or a bacterium?

Ans: Yeast cells are typically larger, have a nucleus, and are eukaryotic, whereas bacteria are smaller, lack a nucleus, and are prokaryotic.

Q6b. What piece of equipment do you need to examine these cells?

Ans: A microscope is required to examine and differentiate yeast and bacterial cells.

Q7a. State the names of the species in figures 3.1 and 3.4.

Ans: Figure 3.1 features dogs, while Figure 3.4 features lions.

Q7b. Describe the variations in two characteristics of these species.

Ans: Dogs vary in size, coat color, and type (e.g., from chihuahuas to German shepherds), while lions vary in mane size and color intensity.

Q8a. Why is a mule a hybrid?

Ans: A mule is a hybrid because it is the offspring of a male donkey and a female horse, two different species.

Q8b. What is a mule not able to do that its parents are able to do?

Ans: Mules are generally sterile and cannot reproduce, unlike their parents.

Q9. Suggest a characteristic of the liger in figure 3.6 that comes from its:

Ans: a) father (lion): Larger size and mane growth.
b) mother (tiger): Striped pattern.

Q10. Suggest why we only find ligers in zoos (and not in the wild).

Ans: Ligergers are bred in captivity as lions and tigers do not share habitats and thus do not meet or mate in the wild.

Q11. Suggest why scientists use scientific names.

Ans: Scientists use scientific names to avoid confusion as common names can vary by region and language; scientific names provide a universal standard.

Q12. In which part of a virus particle are the instructions for making the particle found?

Ans: The instructions are found in the viral genome, which can be made of DNA or RNA.

Q13. During virus replication, what is the source of the proteins needed to build new virus particles?

Ans: The proteins are produced by the host cell, using the genetic instructions from the virus.

Q14. Evaluate the question: Is a self-driving car alive?

Ans: A self-driving car is not alive; it does not meet biological criteria for life such as reproduction, response to environment, growth, or cellular structure.

Q15. Explain why some scientists do not think viruses are living things.

Ans: Some scientists argue that viruses are not living because they cannot replicate independently, lack cellular structure, and do not metabolize on their own, requiring a host cell to reproduce.

Biological Keys

Q1. Identify invertebrates B to F using the key in figure 3.8.

Ans:

• Invertebrate B is a Butterfly (has wings but antennae are not feathered).
• Invertebrate C is a Woodlouse (does not have wings and has more than eight legs).
• Invertebrate D is a Spider (does not have wings and has exactly eight legs).
• Invertebrate E is a Snail (does not have legs but has a shell).
• Invertebrate F is an Earthworm (does not have legs and does not have a shell).

Q1b. You find a new invertebrate with six legs and wings, and antennae that look smooth. Your classmate says it has to be a butterfly. Do you agree? Explain your answer.

Ans: No, I do not agree. According to the dichotomous key, the defining characteristic between a moth and a butterfly is whether the antennae are feathered. Moths have feathered antennae, while butterflies have smooth antennae. Since the new invertebrate has smooth antennae, it would be identified as a butterfly.

Q2. Use the key in figure 3.9 to answer these questions.

• a) Which bird (A to E) is a toucan? Ans: Bird B.
• b) Which bird (A to E) is a scarlet macaw? Ans: Bird E.
• c) What is bird D? Ans: Bird D is a penguin.
• d) What is bird A? Ans: Bird A is a black and white warbler.

Q3. Bird C feeds in shallow lakes and ponds by dipping its beak into the water and filtering out small organisms.

• a) Name this bird. Ans: Bird C is an American flamingo.
• b) Bird F (opposite) is a similar species to bird C. Write two statements for a dichotomous key that would allow you to tell the difference between these two species. Ans:
  • Does the bird have predominantly pink or red plumage? Go to 1.
  • Does the bird have predominantly white plumage with some pink? Bird F.

Q4. Suggest one advantage and one disadvantage of using a dichotomous key to identify something.

Ans: An advantage of using a dichotomous key is its simplicity and efficiency in leading to a correct identification through a series of clear, binary choices. A disadvantage is that it requires observable and clear differences between choices, which may not cover all cases, leading to incorrect identifications if the subject varies slightly from typical descriptions or if the user is inexperienced.

End of Chapter Review

Q1. A characteristic that all mammals have is:

Ans: a) hair

Q2. Grouping organisms with similar characteristics is:

Ans: a) classification

Q3. An animal is placed in the vertebrate group if it has:

Ans: c) a backbone

Q4. Which of the following is not an example of a kingdom?

Ans: a) invertebrates

Q5. Read these word meanings. State the words that match each meaning.

Ans:
(a) Species
(b) Hybrid
(c) Analysis
(d) Data

Q6. Give the names of two groups that the following pairs of animals both belong to.

Ans:
(a) Vertebrates, animals
(b) Arthropods, animals
(c) Invertebrates, animals
(d) Mammals, vertebrates

Q7. Name one kingdom that contains organisms that:

Ans:
(a) Fungi
(b) Animalia
(c) Plantae

Q8. What characteristic of flowering plants does no other plant group have?

Ans: Flowers

Q9. Look at figures 3.14 and 3.15, which both show vertebrates.

Ans:
(a) Animalia
(b) Mammalia
(c) Hair, mammary glands, three middle ear bones
(d) Adaptations to different climates; yak has dense fur for cold weather, cattle less dense fur for varied climates

Q10. Servals and domestic cats are different species. They can, however, breed. Their offspring are called savannah cats.

Ans:
(a) A species is a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
(b) Savannah cats are unable to breed in the wild as servals can; they are largely dependent on human care.

Q11. Use the key in figure 3.16 to identify the three penguin species: A, B, and C.

Ans:
(a) A: King Penguin, B: Macaroni Penguin, C: Chinstrap Penguin
(b) The Galapagos penguin has a pink patch in front of its eye, white feathers under its eye are black and has a pink patch above its eye.

Q12. Look at figure 3.17. Classify organisms W, X, Y and Z. Explain how you make your choices.

Ans: W is an arachnid due to its eight legs; X is an insect due to its six legs and segmented body; Y is a crustacean due to its ten legs and shell-like body; Z is an insect due to its six legs and antenna.

Q13. List two groups of vertebrates that:

Ans:
(a) Amphibians and fishes
(b) Reptiles and fishes

Q14. Look at the dinosaurs below. Design a key to allow others to identify the different dinosaurs.

Ans: 1. Check if the dinosaur has a horn on its nose – Go to 2; No horn – Go to 3.
2. Horn pointing up – Triceratops; Horn pointing down – Stegosaurus.
3. Long tail and stands on two legs – Tyrannosaurus Rex; Long tail and stands on four legs – Brachiosaurus.

End of stage review

Q1. (a) (i) The table shows some parts of a cell and some functions of parts of a cell. Copy the table and complete the missing information.

Ans:

Q1. (a) (ii) Explain how you know that this is a plant cell.

Ans: This is a plant cell because it contains chloroplasts, which are specialized for photosynthesis and are typically found only in plant cells.

Q1. (b) (i) Which life process is shown in the graph?

Ans: The life process shown in the graph is growth.

Q1. (b) (ii) How tall was tree A after four years?

Ans: After four years, Tree A was approximately 3 meters tall.

Q1. (b) (iii) Explain how you can tell which tree showed the fastest growth.

Ans: Tree D showed the fastest growth because it has the highest curve on the graph over the 10 years, indicating it grew taller than the other trees in the same period.

Q1. (b) (iv) As the height of a tree increases, what happens to the cells? Choose one correct answer:

Ans: c. the number of cells increases

Q1. (c) (i) What is the function of a red blood cell?

Ans: The primary function of a red blood cell is to carry oxygen throughout the body.

Q1. (c) (ii) Explain what parts red blood cells do not have, which other cells in your body do have.

Ans: Red blood cells lack a nucleus and other organelles like mitochondria, which are present in most other cells.

Q1. (c) (iii) Explain why blood is sometimes described as a liquid organ.

Ans: Blood is described as a liquid organ because it is a collection of different cells that perform specific functions, flowing throughout the body to transport nutrients, oxygen, and waste.

Q2. (a) (i) Make a prediction about what will happen in jars A and B. Explain your predictions.

Ans: In Jar A (open jar), maggots will appear because flies can enter and lay eggs on the meat. In Jar B (jar with a lid with small holes), maggots are unlikely to appear as flies cannot access the meat to lay eggs.

Q2. (a) (ii) What was the name of this scientist?

Ans: The scientist was Francesco Redi.

Q2. (a) (iii) Make a prediction about what will happen in flasks C and D. Explain your predictions.

Ans: In Flask C, no microbial growth will occur because boiling kills microbes and the sealed setup prevents new microbes from entering. In Flask D, microbial growth may occur after the neck is broken, exposing the contents to air.

Q3. (a) (i) Describe how two characteristics vary in these foxes.

Ans: The Arctic fox (X) has thick white fur, suitable for camouflage and warmth in snowy environments. The red fox (Y) has medium thickness red fur, adapted for temperate environments. The desert fox (Z) has thin brown fur, ideal for hot, arid climates.

Q3. (a) (ii) What is a species?

Ans: A species is a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.

Q4. Use the key to identify butterflies A and B.

Ans: Butterfly A is identified as a Monarch due to its mainly orange and black body. Butterfly B is identified as a Dark Kite Swallowtail because it has two white stripes in its head region only and no tails on hind wings.