EXCRETION

Homeostasis

To understand excretion, we need to understand homeostasis –

Homeostasis

To understand excretion, we need to understand homeostasis – the ability to maintain a constant system in the face of fluctuations in the environment.

Homeostasis

To understand excretion, we need to understand homeostasis – the ability to maintain a constant system in the face of fluctuations in the environment.

If I ate a whole block of chocolate – instead of giving me a diabetic coma, my body balances out my blood sugar level.

Excretion

The removal of waste and excess products of the metabolism of the cells.

Excretion

The removal of waste and excess products of the metabolism of the cells.

Excretory products are water, carbon dioxide, and excess minerals.

Excretion

The removal of waste and excess products of the metabolism of the cells.

Excretory products are water, carbon dioxide, and excess minerals.

Kidneys are a very important organ for excretion, along with the lungs, skin and hormones.

Nitrogenous wastes

Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration.

Nitrogenous wastes

Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration.

These produce leftover fragments of nitrogen compounds which can be extremely poisonous.

Nitrogenous wastes

Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration.

These produce leftover fragments of nitrogen compounds which can be extremely poisonous.

Amino acid ammonia + acid

urea carbohydrates etc

Nitrogenous wastes

Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals.

Nitrogenous wastes

Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals.

Urea – toxic but not as bad as ammonia. Can be stored in body temporarily. Must be flushed out with lots of water. Animals that use this method must drink lots.

Nitrogenous wastes

Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals.

Urea – toxic but not as bad as ammonia. Can be stored in body temporarily. Must be flushed out with lots of water. Animals that use this method must drink lots.

Uric Acid – non-toxic, excreted as a pasty substance or as crystals. Important with eggs of birds/reptiles as the wastes don’t poison growing embryo.

Excretion in Invertebrates

Amoeba- Excrete ammonia directly into the surrounding water by simple diffusion.

Excretion in Invertebrates

Amoeba- Excrete ammonia directly into the

surrounding water by simple diffusion. - Also have a contractile vacuole to pump

out excess water.

Excretion in invertebrates

Earthworms- Use nephrida tubules – cleans the fluids in the segment previous.

Excretion in invertebrates

Earthworms- Use nephrida tubules – cleans the fluids

in the segment previous. - Any fluid passing through the tubules

has close contact with a network of blood capillaries.

Excretion in invertebrates

Earthworms- Use nephrida tubules – cleans the fluids

in the segment previous. - Any fluid passing through the tubules

has close contact with a network of blood capillaries.

- Water and minerals are absorbed into the blood and wastes are passed to the outside through a nephridiopore.

Excretion in invertebrates

Insects- Malphigian tubules connected to the

area where the mid-gut and the hind-gut join.

Excretion in invertebrates

Insects- Malphigian tubules connected to the

area where the mid-gut and the hind-gut join.

- These float in body fluid where they absorb nitrogenous waste – converting them to uric acid

Excretion in invertebrates

Insects- Malphigian tubules connected to the

area where the mid-gut and the hind-gut join.

- These float in body fluid where they absorb nitrogenous waste – converting them to uric acid

- As digestive wastes pass down the gut, these tubules pass the crystals into the gut and they are excreted as faeces.

Osmoregulation

Freshwater fish- Constant danger of drowning

Osmoregulation

Freshwater fish- Constant danger of drowning- Also lose a lot of salt

Osmoregulation

Freshwater fish- Constant danger of drowning- Also lose a lot of salt- Kidneys of these fish actively reabsorb

salt and let through all the water, so they have a large, watery urine.

Osmoregulation

Freshwater fish- Constant danger of drowning- Also lose a lot of salt- Kidneys of these fish actively reabsorb

salt and let through all the water, so they have a large, watery urine.

Osmoregulation

Marine fish- Problems losing water as their blood is less salty than the sea water (hypotonic)

Osmoregulation

Marine fish- Problems losing water as their blood is

less salty than the sea water (hypotonic)- Many drink sea water

Osmoregulation

Marine fish- Problems losing water as their blood is

less salty than the sea water (hypotonic)- Many drink sea water- These fish get rid of excess salt through

special glands in the gills and give out small amounts of urine.

Osmoregulation

Sharks and rays- Keep urea in their blood so that it is

stronger than the sea water.

Osmoregulation

Sharks and rays- Keep urea in their blood so that it is

stronger than the sea water.- They get rid of excess salt through

special glands in the intestine and excreting it through the kidneys.