Further Up the Food Chain
Most living things cannot produce their own food, these organisms are called - heterotrophs., and have a variety of feeding relationships.
- When both organisms benefit from the relationship it is called MUTUALISM. Eg. the clown fish and the anemone have a close relationship.
Parasites - Organisms that feed off others without offering anything in return are called PARASITES.
Heterotrophs all rely on getting ready made organic compounds to provide their food.
One sided relationships:- Only one species benefits from the relationship, but the other is unharmed.
Tape-worms and other Parasites
Life on earth exists on land, in water and also on or in other living things.
Human parasites: they have sevreal ways of being trasferred into a human body:
- by food or water
- through the nose, mouth, anus and urinary tracts.
- by insects bites
- by burrowing under the skin.
Human parasites are TAPEWORMS, they live in the human gut and can be up to 9m long, the human tapeworm competes it's host for digested food.
Parasites have specific features which enable them to survive in or on their host. Tapeworms have a number of adaptions:-
-Their heads have suckers and stickers to the grip wall and the gut wall.
- They are protected from the digestion by a thick, enzyme- resistant cuticle.
- They use anaerobic repirtation so that they can survive without oxygen.
- Each tapeworm has male and female sex organs so it can reporduce without a mate.
-They produce a large number of eggs, increases the chances of survival also to find a new host.
Parasites that can cause diseases
The disease malaria is a major is a major cause of ill health and death in countries.
Malaria is caused by PROTOZOAN.
The protozoan parasite is a single-cell animal cell. Blood sucking mosquitoes carry this protozoan from host to host. Malaria kills more than 2 million people in a year.
The malaria parasite's life cycle protects it from our immune system. The parasites have different markers on their cells at every stage of the life cycle. This makes it difficult for white blood cells to identify and attack them. Parasites spend most time feeding on RED BLOOD CELLS.
When one red blood cell is used up the parasites burst out and infect new cells. Toxins are released from the used up cells, and cause a dangerous fever.
Sickle Cell Anaemia
Sickle cell anaemia is a genetic disorder, caused by a faulty gene which codes for the haemoglobin - this is a protein that carries oxygen molecules in red blood cells.
Sickle cell haemoglobin proteins have different shapes from the normal haemoglobin. When faulty haemoglobin gives up oxygen to blood cell, the shape of the haemoglobin molecule changes.
The haemoglobin form long rods which stretch red blood cells into a rigid 'sickle' shape. They get stucj in small blood vessels causing acute pain and tiredness. Body do not get the oxygen they need so overtime damages tissues and organs.
'Sickling' also damages red blood cells, and cannot be replaced fast enough.
How sickle cell anaemia is inherited
The sickle cell allele is RECESSIVE.
A person must inherit it from both parents in order to get the disease.
A person with one sickle cell allele and one normal allele is a carrier of sickle cell aneamia.
Sickle Cell and Anaemia:-
The sickle cell allele occurs occasionaly as a random mutuation.