Section 1: The nature and variety of living organisms

Question 1

What characteristics do all living things need?

Answer 1

Movement
Reproduction
Sensitivity

Nutrition
Excretion
Respiration
Growth

Question 2

What are the features of an animal?

Answer 2

• They are multicellular organisms
• there cells do not contain chloroplasts
• they are not able to carry out photosynthesis
• they have no cell walls
• they usually have nervous coordination and are able to move one place to another
• they often store carbohydrate as glycogen
  This includes mammals - humans, insects - horsefly and mosquito

Question 3

What are the features of a plant?

Answer 3

• they are multicellular organisms
• their cells contain chloroplasts
• they are able to carry out photosynthesis
• their cells have cellulose cell walls
• they store carbohydrates as starch or sucrose
  Examples include: flowering plants, such as cereal (eg maize) and herbaceous legume (eg peas and beans)

Question 4

What are the features of fungi?

Answer 4

• they are organisms
• they are not able to carry out photosynthesis
• their body is usually is organised into a mycelium made from thread-like structures called hyphae, which may contain many nuclei
• their cell have walls made of chitin
• they feed by extracellular secretion of digestive enzymes onto food material and absorption of organic products, this is know as saprotrophic nutrition
• they may store carbohydrates as glycogen
  Examples include Mucor, which has the typical fungal hyphal structure, and yeast, which is single - celled

Question 5

What are the features of bacteria?

Answer 5

• These are microscopic single- celled organisms
• they have a cell wall, membrane, cytoplasm and plasmids
• 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
  Examples include: lactobacillus bulgaricus, a rod- shaped bacterium used in the production of yoghurt from milk, and pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia.

Question 6

What are the features of protoctists?

Answer 6

• These are microscopic single- celled organisms
• Some, like Amoeba, that live in pond water, have features like an animal cell, while other like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria.

Question 7

What are the features of viruses?

Answer 7

• these 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
  Examples include the tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes ‘flu’ and the HIV virus that causes AIDS