Section 1: b) Variety of Living Organisms Flashcards
What is classification?
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.
Why is classification important to biologists?
It helps them to order and categorise all forms of life and understand the relationships between different organisms.
What are the five kingdoms that living organisms are divided into?
Plants, Animals, Fungi, Bacteria (prokaryotes), Protoctists
Which organisms are eukaryotic?
Plants, animals, fungi and protoctists
Which organisms are prokaryotic?
Bacteria
What are the main characteristics of plants?
~Multicellular organisms.
~Cells contain chloroplasts and are able to carry out photosynthesis.
~Cells have cellulose cell walls.
~Store carbohydrates as starch/sucrose.
Give examples of organisms belonging to the plant kingdom.
Herbaceous legume e.g. peas, beans
Flowering plants, such as a cereal e.g. maize
What are the main characteristics of animals?
~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.
Give examples of organisms belonging to the animal kingdom.
Mammals e.g. humans
Insects e.g. housefly, mosquito
What are the main characteristics of fungi?
~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.
Give examples of organisms belonging to the fungi kingdom.
Mucor (multicellular; has the typical fungal hyphal structure)
Yeast (unicellular)
What features does a typical fungal cell have in common with plant and animal cells?
A typical fungal cell has cytoplasm, ribosomes, mitochondria, a nucleus, cell membranes and cell walls in common with plant and animal cells.
Multicellular fungi have hyphae. What are hyphae and what is their purpose?
Hyphae are fine thread-like filaments with lots of nuclei. They secrete digestive enzymes onto their food, and then absorb the soluble substances produced.
What are the main characteristics of the protoctists kingdom?
~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.
What is a mycelium?
A mycelium is a network of hyphae.
Give examples of organisms belonging to the protoctists kingdom.
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
Why might scientists be tempted to classify Chlorella as a plant?
They contain chloroplasts, which means they can photosynthesise; this is a characteristic of a plant.
What are the main characteristics of the bacteria kingdom?
~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.
Give examples of organisms belonging to the bacteria kingdom.
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
What is a pathogen?
A pathogen is a disease-causing organism.
Which organisms are pathogens?
Fungi, bacteria, protoctists and viruses
What are the main characteristics of viruses?
~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.
Give examples of organisms which are classed as viruses.
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.
Why aren’t viruses included as a 6th kingdom?
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.