Section 1: b) Variety of Living Organisms

Question 1

What is classification?

Answer 1

There are so many different kinds of living organisms that come in different shapes and sizes. They can be classified into groups according to their observable features and characteristics.

Question 2

Why is classification important to biologists?

Answer 2

It helps them to order and categorise all forms of life and understand the relationships between different organisms.

Question 3

What are the five kingdoms that living organisms are divided into?

Answer 3

Plants, Animals, Fungi, Bacteria (prokaryotes), Protoctists

Question 4

Which organisms are eukaryotic?

Answer 4

Plants, animals, fungi and protoctists

Question 4

Which organisms are prokaryotic?

Answer 4

Bacteria

Question 6

What are the main characteristics of plants?

Answer 6

~Multicellular organisms.
~Cells contain chloroplasts and are able to carry out photosynthesis.
~Cells have cellulose cell walls.
~Store carbohydrates as starch/sucrose.

Question 7

Give examples of organisms belonging to the plant kingdom.

Answer 7

Herbaceous legume e.g. peas, beans

Flowering plants, such as a cereal e.g. maize

Question 8

What are the main characteristics of animals?

Answer 8

~Multicellular organisms.
~Cells do not contain chloroplasts and are not able to carry out photosynthesis.
~No cell walls.
~Usually have nervous co-ordination and are able to move from one place to another.
~Often store carbohydrates as glycogen.

Question 9

Give examples of organisms belonging to the animal kingdom.

Answer 9

Mammals e.g. humans

Insects e.g. housefly, mosquito

Question 10

What are the main characteristics of fungi?

Answer 10

~They are multicellular organisms (e.g. mushrooms, toadstools and moulds) except yeasts which are unicellular.
~They have cell walls made of chitin.
~Multicellular fungi contain hyphae.
~They are not able to carry out photosynthesis and so feed by extracellular secretion of digestive enzymes onto food material and absorption of organic products (saprotrophic nutrition).
~They may store carbohydrates as glycogen.

Question 11

Give examples of organisms belonging to the fungi kingdom.

Answer 11

Mucor (multicellular; has the typical fungal hyphal structure)

Yeast (unicellular)

Question 12

What features does a typical fungal cell have in common with plant and animal cells?

Answer 12

A typical fungal cell has cytoplasm, ribosomes, mitochondria, a nucleus, cell membranes and cell walls in common with plant and animal cells.

Question 13

Multicellular fungi have hyphae. What are hyphae and what is their purpose?

Answer 13

Hyphae are fine thread-like filaments with lots of nuclei. They secrete digestive enzymes onto their food, and then absorb the soluble substances produced.

Question 13

What are the main characteristics of the protoctists kingdom?

Answer 13

~They are microscopic organisms (that don’t fit into any of the other categories).
~Most are unicellular although algae such as seaweeds are multicellular.
~ They can have features of both animal and plant cells.
~They are usually aquatic.

Question 14

What is a mycelium?

Answer 14

A mycelium is a network of hyphae.

Question 15

Give examples of organisms belonging to the protoctists kingdom.

Answer 15

Amoeba, which live in pond water and have some features like an animal cell

Chlorella, which have chloroplasts and are more like plants

Pathogenic example-Plasmodium, responsible for causing malaria

Question 16

Why might scientists be tempted to classify Chlorella as a plant?

Answer 16

They contain chloroplasts, which means they can photosynthesise; this is a characteristic of a plant.

Question 17

What are the main characteristics of the bacteria kingdom?

Answer 17

~They are microscopic single-celled organisms, which can be different shapes.
~They have a cell wall, cell membrane, cytoplasm and plasmids (small circular loops of DNA separate from the main bacterial chromosome).
~They lack a nucleus but contain a circular chromosome of DNA.
~Some bacteria can carry out photosynthesis but most feed off other living or dead organisms.

Question 18

Give examples of organisms belonging to the bacteria kingdom.

Answer 18

Lactobacillus bulgaricus, a rod-shaped bacterium which is used in the production of yoghurt from milk, to prevent diarrhoea and aid digestion

Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia

Question 19

What is a pathogen?

Answer 19

A pathogen is a disease-causing organism.

Question 20

Which organisms are pathogens?

Answer 20

Fungi, bacteria, protoctists and viruses

Question 21

What are the main characteristics of viruses?

Answer 21

~They are not living organisms.
~They are small particles, smaller than bacteria.
~They are parasitic and can reproduce only inside living cells.
~They infect every type of living organism.
~They have a wide variety of shapes and sizes.
~They have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA.

Question 22

Give examples of organisms which are classed as viruses.

Answer 22

Tobacco mosaic virus, which causes the discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts

Influenza virus, which causes ‘flu’

HIV virus, which causes AIDS.

Question 24

Why aren’t viruses included as a 6th kingdom?

Answer 24

They reproduce using the host cell’s ‘machinery’, obtain nutrients from the host cell, have no metabolism, cannot excrete and cannot exist on their own. Overall, scientists class them as non-living.