Edexcel IGCSE Biology - Living Organisms and Cells (3.1 )

Topics

• Understanding that living organisms share the following characteristics:
  they require nutrition
  they respire
  they excrete their waste
  they respond to their surroundings
  they move
  they control their internal conditions
  they reproduce
  they grow and develop

• Describing the levels of organisation within organisms: organelles, cells, tissues, organs and systems

• Describing cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplast, ribosomes and vacuole

• Describing the functions of the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes and vacuole

• Knowing the similarities and differences in the structure of plant and animal cells

• Describint the common features shown by eukaryotic organisms: plants, animals, fungi and protoctists

• Plants: these are multicellular organisms; their cells contain chloroplasts and 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 a cereal (for example,maize), and a herbaceous legume (for example, peas or beans).

• Animals: these are multicellular organisms; their cells do not contain chloroplasts and are not able to carry out photosynthesis; they have no cell walls; they usually have nervous co-ordination and are able to move from one place to another; they often store carbohydrate as glycogen. Examples include mammals (for example, humans) and insects (for example, housefly and mosquito).

• Fungi: these are organisms that are not able to carry out photosynthesis; their body is usually organised into a mycelium made from threadlike structures called hyphae, which contain many nuclei; some examples are single-celled; their cells have walls made of chitin; they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition; they may store carbohydrate as glycogen. Examples include Mucor, which has the typical fungal hyphal structure, and yeast, which is single-celled.

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