Excretion

Question 1

Define excretion:

Answer 1

• Removal of waste products by an organism
• regulates internal environment:
  
  • controls cell/body water content
  • maintenance of solute composition
  • excretion of metabolic waste products

Question 2

Define secretion:

Answer 2

Movement of material that has specific task after leaving the cell or organism

Question 3

Define elimination:

Answer 3

removal of unabsorbed food that has never been a part of the body (usually as facaes)

Question 4

What would happen if excretion did not occur?

Answer 4

Disruption of cell membranes, inefficient metabolism, death.

Question 5

Define passive transport:

Answer 5

• where solutes cross the membrane w/o the involvement of a specific transport system.
• movement of solutes due to a chemical gradient of a solute through osmosis and diffusion
• bacteria, fungi, some aquatic plants.

Question 6

Define the role of active transport:

Answer 6

• Systems to gain substances ___ in the opposite direction.
• Most species have specialised cells or organs that evolved to assist w/ excretion and elimination
• active transport of waste products allows for organisms to be larger and more complex in size.

Question 7

What are guard cells? Explain there function.

Answer 7

• located on the outer surface of leaves and stems.
• produce in pairs w/ a gap between them (stomatal pore).
• Involved in gas exchange and assist w/ controlling water loss.
• Stomatal pores open most when the plant has lots of water and the guard cells are swollen.
• The stomatal pores close when water availability is low and the guard cells shrink.

Question 8

What are flame cells? Explain their function.

Answer 8

• specialised excretory cells found in freshwater invertebrates.
• FC = function like a mammalina kidney (removing wastes).
• Bunelle of flame cells = protonephrida
• early animals have pro…
• later animals have more complex nephrida along with associated glands.
• vertebrates have kidneys and a liver along w/ associated glands.

Question 9

What is the coelom:

Answer 9

• Fluid filled - internal support
• separates internal processes from gut
• allows transport of fluids
• provides space for internal development of internal organs
• enables increased body size.

Question 10

Detail the excretion of protists and early euks:

Answer 10

• simple celled orgs have just the one cell to play with and there are no specialised organs
• majority of waste and biproducts of metabolism are eliminated by passive diffusion and osmosis.
• active transport of waste (chemicals) occurs through specialised membrane channels and/or are expelled directly.

Question 11

How do amoeba excrete?

Answer 11

• phagocytose food particles in a vacuole, excrete enzymes to digest it, release waste in a reverse process (exocytosis)

Question 12

Explain the process in which fungi excretes waste:

Answer 12

• specialised organs
• some waste and biproducts of metabolism are eliminated by passive diffusion or osmosis.
• Active transport of wastes occurs through specialsed cell membrane channels and are expelled directly using a comparable method to bacteri (exocytosis w/ food vacuoles, contraticle vacuoles).

Question 13

What are the 3 key mechanisms of a plant?

Answer 13

1. Transpiration: waste excreted through stomata as the stem and outer surface of the stem.
2. Storing: storing in bark or leaves.
3. Excreting metabolic wastes through diffusion.

Question 14

Explain the process of transpiration:

Answer 14

• transpiration = day
• Guttation = night
• drops of xylem spa gather on the tips pr edges pf plants (some fungi)
• water builds up at night due to root pressure.

Question 15

Explain how waste is stored in plants:

Answer 15

• plants produce waste materials that get accumlated in the vacuoles of opening cells.
• stems, leaves, or bark of trees
• cells eventually die and fall off the plant.
• excretion gets rid of potentially toxic substances.
• can be manipulated by humans (rubber or maple syrup).

Question 16

Explain the role of diffusion in plants:

Answer 16

• water and nutrients move in from root hair cells.
• root hair cells are partially permeable(high conc –> low conc)
• diffusion through roots in plants also, important to expell wastes
• root hair increase SA/V ratio.

Question 17

Explain how Nitrogenous waste is excreted (and why this is important):

Answer 17

• heterotrophs eat lots of proteinleading to increased N intake.
• N –> ammoni, urea, uric acid, and guanine.
• aquatic animals = ammonia.
• land animals = urea/uric acid
• spider = guanine

Question 18

What is ammonia?

Answer 18

One N per molecule, needs lots of water for excretion bc highly toxic. Very soluble.

Question 19

What is urea?

Answer 19

2N per molecule, less toxic, less water, synthesis more complex (uses more ATP (4)).

Question 20

What is uric acid?

Answer 20

4N per molecule, increased insolubility, non-toxic, excretion conserves water, synthesis more complex (uses more ATP (24)).

Question 21

What is guanine?

Answer 21

5N PER MOLECULE, Nearly insoluble, little water loss, VERY high energy cost.

Question 22

What are the different types of excretory organs for diff orgs?

Answer 22

• Annelids = coelem –> exterior
• Protenephridia –> nephrida –> ___ tublue system (increasing complexity)
• Insects = hindgut for excretion + elimination.
• Vertebrates = kidney and liver.