2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.

Organelles à  Cells à Tissues à Organs à Organ systems

Organelles – Specialised structures that carry out a particular function within a cell (intracellular). They are made out of highly organized structures of molecules.

 

     E.g. Chloroplast – absorbs light to complete photosynthesis. 

Cells- Basic structural and functional unit from which organisms are made off, also known as the “building blocks of life”. Cells are made out of organelles.

Tissue – Group of specialized cells with similar structures and the same origin, which work together to carry out a specific function.

Organ – Structure made out of a group of tissues, which work together and are adapted to perform a specific function in an organism.

 

     E.g. The heart, its function is to pump blood around the body

Organ system – Group of several organs (with related functions) which work together to carry out a specific function.

 

    E.g.  The circulatory system includes blood vessels and the heart 

1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria, protoctists or viruses.

Pathogens

A pathogenic organism is a micro-organism capable of causing disease to its host or to another organism. The following kingdoms are pathogenic;

• The Fungi Kingdom
• The Bacteria Kingdom
• The Protoctist Kingdom
• Viruses (In a host cell)

1.2 describe the common features shared by organisms within the following main groups: plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe examples and their features

Main Groups of Organisms 

• Plants
• Animals 
• Fungi
• Bacteria 
• Protoctists
• Viruses 

Plants

• Multicellular organisms
• Cells contain chloroplast and are able to carry out photosynthesis
• Cells have cellulose cell walls
• They store carbohydrates as starch or sucrose

Examples include flowering plants, such as cereal (e.g. maize) and a herbaceous legume (e.g. peas or beans)

Animals

• Multicellular organisms
• Cells do not contain chloroplast and are not able to carry out photosynthesis
• Cells do not contain cell walls
• They usually have a nervous coordination and are able to move from one place to another 
• They often store carbohydrates as glycogen 

Examples include mammals (e.g. humans) and insects (e.g. mosquito) 

Fungi

• Usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei (multicellular)
• Some examples are single-celled
• They are saprophytic and feed by excreting digestive enzymes onto food and absorbing the digested products (saprotrophic nutrition)
• Their cells have walls made of chitin (a protein)
• They store carbohydrates as glycogen

Examples include Mucor (hyphal/multicellular) and yeast (single cell)

Bacteria

• These are microscopic single-celled organisms
• They don’t have a nucleus but contain a circular chromosome of DNA (a bacterial chromosome)
• Some bacteria can carry out photosynthesis, but most are saprophytes and feed of dead organisms
• They have a cell wall, cell membrane, cytoplasm and plasmids

Examples include Lactobacillus bulgaricus (a rod-shaped bacterium used in the production of yoghurt from milk) and Pneumococcus (a spherical bacterium that causes Pneumonia) 

Protoctisis

• Everything else that doesn’t fit in any of the other kingdoms
• They can be single-celled and multicellular organisms

Some like Amoeba that live in pond water, have animal characteristics
Some like Chlorella have chloroplast and have plant characteristics
A pathogenic example is Plasmodium, responsible for causing malaria 

Viruses

• Not living organisms 
• The small particles, smaller than bacteria, not made out of cells
• They are parasitic and can only reproduce inside living cells (host cells)
• They can infect every type of  living organisms
• They do not have a cellular structure but have a protein coat and contain one type of nucleic acid,  either DNA or RNA

Examples include the tobacco mosaic virus, the influenza virus (causes “flu”) and the HIV virus (causes AIDS)

1.1 Understand that living organisms share the following characteristics:

MRS C-GREN 

• Movement – The ability to move from one place to another, by the action of muscles in animals or growth movement in plants
• Respire – Get energy from food
• Sensitivity (respond to stimuli) – Sensitive to changes in the environment  e.g. react to high temperature or the amount of light 
• Control their internal conditions – Maintain constant internal environment, homeostasis
• Growth and develop – Increase in size and mass and become stronger by cell division  
• Reproduce – Produce offspring, more living things of the same type
• Excrete – Getting rid of toxic waste products
• Nutrition – Taking in food or producing their own food

2.57 describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

Plasma -  A yellow liquid which is mainly made of water (good solvent). The function of plasma is to carry blood cells, waste products, hormones and dissolved nutrients. Plasma also distributes heat to maintain the body temperature. It makes up 55% of the blood.

Red Blood Cells (erythrocytes) - Cells with a biconcave shape and no nucleus. Red blood cells contain hemoglobin, a red pigment that combines with oxygen to form the compound oxyhemoglobin. The function of red blood cells is to carry oxygen from the lungs to all the cells in the body (for respiration). Red blood cells make up 45% of the blood.

White Blood Cells - The function of white blood cells is to protect the body against pathogens. White blood cells make up less than 1% of the blood. There are two types of white blood cells, these are phagocytes and lymphocytes. 

• Phagocytes engulf pathogens by trapping them in a vacuole and then digests (breaks down) them using enzymes.
• Lymphocytes produce antibodies (specific to the pathogen) to destroy the microorganism.
• Memory lymphocytes give us immunity to specific diseases. 

Platelets - The function of platelets is to release chemicals in order to make a blood clot. This prevents further blood loss and the entry of pathogens into the body. Platelets are fragments of larger cells which are produced in the bone marrow. Platelets make up less than 1% of the blood.