Ch8: Nutrition & Excretion

Question 1

Define what a detrivore is?

Answer 1

Organisms that consume dead/decaying organic material to acquire their nutrients - often aid primary producers

Question 2

Define what an autotroph is (what are the 2 different kinds)?

Answer 2

Autotrophs: organisms that are able to harness/produce their own necessary energy and nutrients

Chemoautotrophs: oxidise inorganic molecules to organic energy compounds to produce essential nutrients

Photoautotrophs: get their nutrients by utilising energy from sunlight

Question 3

Define heterotrophs:

Answer 3

Must get their energy from other organisms (autotrophs or other heterotrophs)

Question 4

Hydrothermal vents: hosts?

Answer 4

Hosts use inorganic compounds to fix CO2

Question 5

What are the adaptations of heterotrophs that allow them to gain nutrients: (hint there are 3)

Answer 5

1) Capture/collection of prey

2) Mechanical + chemical digestion

3) Absorption (and assimilation of key nutrients into the body)

Question 6

Name some morphological traits of animals: (hint there are 4)

Answer 6

1) Different teeth/positioning

2) Different jaws

3) Mouthparts (in insects for sucking liquid)

4) Limb modification

Question 7

What are organic nutrients vs inorganic nutrients? Why are nutrients important?

Answer 7

Organic: carbon based molecules

Inorganic: minerals

Important: needed for growth and homeostasis

Question 8

Define essential nutrients

Answer 8

Nutrients required for the life cycle of an organism (plant) that they cannot produce themselves

Question 9

What are macronutrients? Give some examples and their roles;

Answer 9

Nutrients required for large proportions;

Carbon: necessary for nucleic acids, proteins + carbohydrates

Nitrogen: necessary for nucleic acids, proteins + chlorophyll

Potassium: regulating gas exchange (+ photosynthesis)

Question 10

What are micronutrients? What is their other role?

Answer 10

Required in smaller proportions;
They can function as cofactors for enzymes

Question 11

What are polysaccharide and disaccharides?

Answer 11

Poly: chain of glucose (hydrolysed to glucose) and used in pyruvate, NADH and ATP

Di: sugar that is broken down in 2 simpler sugars (glucose + fructose)

Question 12

What are the roles of rhizobacteria or fungi (mycorrihizae)?

Answer 12

They fix atmospheric nitrogen into something biologically useful for plants.

Question 13

What kind of relationship is the one between nitrogen fixing agents and plants? What does the fixing agent gain from this relationship and what does it do?

Answer 13

Symbiotic relationship

GAIN:
- produces antibiotics to protect the plant (acts as a physical barrier)
- absorbs unwanted chemicals from the soil
- facilitates the acquisition of essential nutrients (fixes N2 –> NH4 (ammonium) or NO3 (nitrate)

Question 14

Where does nitrogen fixation occur in legumes?

Answer 14

Nodules on their roots

Question 15

Why does a plant need to get rid of its waste products?

Answer 15

To maintain homeostasis (these wastes are generally recycled)

Question 16

How does plant waste removal occur? What does this cause? (hint: has to do with pressure in leaves)

Answer 16

Occurs via transpiration of the stomata

This transpiration generates pressure in leaves and causes water to be brought up the XYLEM. Hence the roots begin to take up more water

Causes stomatal openings need to be regulated; some plants keep their pores permanently open pores (LENTICELS) to remove wastes

Question 17

What is stomatal opening regulated by?

Answer 17

CO2, humidity, light, stress hormone (abscisic acid)

Question 18

What happens to nitrogen waste, and how is nitrogen absorbed by the plant?

Answer 18

It is absorbed through the plants xylem sap.

nitrogen waste occurs due protein metabolism, BUT a lot of it can be RE-USED in protein synthesis for growth and development

Question 19

What are the 2 types of nitrogen removal? describe them

Answer 19

1) Shedding; method of waste removal
- plants can store unwanted waste products in VACUOLES of the cell (amino acids, water, mineral salts)
- the wastes are shed as fruits, bark or leaves

2) Guttation: at night stomata close (prevent H2O)
- This leads to an accumulation of H2O as ROOT PRESSURE causes roots to continue to absorb H2O
- To excrete this excess water some plants can excrete water and minerals in small droplets of XYLEM SAP from leaf margins; goes through secretory cells (HYDATHODES - modified stomata cells)

Question 20

How do fungi absorb their food (hint: there are 2 ways)

Answer 20

1) small soluble molecules can simply diffuse into the hyphae

2) large insoluble molecules need to undergo PRELIMINARY digestion: exudation of enzymes that break them down

Question 21

Define the circulatory system:

Answer 21

transportation of essential vitamins, minerals, and macromolecules around the body

Question 22

Define the digestive tract

Answer 22

A highly vascularised system - depends on what food is consumed by that organism for what level of vascularisation

Question 23

Define what a simple gut is

Answer 23

Simple organisms:
- They have gastrovascular cavities allow for food to enter, and the walls are lined with cells that produce digestive enzymes

Ex~ sponges with open channel to absorb food particles

Question 24

Define the 3 sections of the gut

Answer 24

1) Foregut: initial stages of chemical and mechanical digestion + storage and intake of food

2) Midgut + Hindgut:
- Mainly chemical digestion + absorption of nutrients prior to evacuation of water

Question 25

Describe the diet of herbivores

Answer 25

Food: low energy, hard to digest

Question 26

How does the foregut of a herbivore digest?

Answer 26

Chemical: has acids and digestive enzymes

Mechanical: contract/churn to expose to chemicals

Question 27

Define/describe foregut fermenters:

Answer 27

Have 4 sections to the foregut;
- Rumen, reticulum,
omasum, abomasum

See Doc, 8a:
They first ‘take’ food to rumen to begin chemical + mechanical digestion
- They regurgitate their food to continue mechanical digestion and then bring it back through the foregut to be fermented by microbes

Question 28

Define/describe hindgut fermenters:

Answer 28

See Doc, 8b:
Have a simple stomach;
- Have long hindguts to lengthen digestion
- These lead to a caecum (winding that is lined) with microbes to ferment the plant food

Question 29

Adaptations of carnivores have to eat their food. Why do they have these adaptations?

Answer 29

they have sharper/serrated curved teeth to help shred tissue (mechanical digestion)

Tissue is easier to break down: so they rely on chemical digestion

Question 30

Trends of carnivorous guts compared to herbivores?

Answer 30

Normally have shorter less complex guts
- The stomaches = acidic and are effective for protein digestion (foregut)
- Midgut = where lipid digestion occurs (where special bile is secreted)

Question 31

How do organisms maximise their SA in the gut? (Hint: there are 3 things)

Answer 31

1) Have foldings in the gut = increased SA

2) Have extra tissue structures = increased SA

3) Villi (adsorptive tissues) have microvilli (small extending tubes) = increased SA

Question 32

What is nitrogenous waste converted to? What about this waste makes it significant?

Answer 32

Nitrogen is converted to ammonia, which is highly toxic

Question 33

How do marine animals, land mammals, and birds, insects + reptiles excrete nitrogenous waste?

Answer 33

1) Marine animals: directly excrete the ammonia as they have ample access to water to dilute ammonia

2) Do not have enough access to water to directly release ammonia so they convert it to UREA (requires ENERGY), but conserves water as urea (is LESS toxic)

3) Convert it to uric acid (solid form) which requires MORE energy, but less water

Question 34

What does:
1) Water-solubility of urea allow for:

2) Solid-nature of uric acid:

Answer 34

1) Water-solubility of urea: allows mammalian embryos to remove waste in their mother’s blood

2) Allows waste from bird embryos to form harmless lamps in eggs, which have had shells that urea could NOT pass through

Question 35

How do marine organisms excrete nitrogen through their body walls:

Answer 35

Unspecialised;
- Some do have specialised systems
- The flatworms have excretory pores connected to tubules that end in flame cells (cilia going into tubule) (PROTONEPHRIDIA)

Question 36

Define metanephridia

Answer 36

See Doc, 8c:
Tubules that connect to the sac around (pericardium) the heart that contains nitrogenous waste
- The tubules take this waste into the mantle cavity to be released as urine

Question 37

Describe how aquatic vertebrates mostly excrete via the kidney and its functional unit (NEPHRON):

Answer 37

See Doc, 8d:
1) Filtration: the blood vessels interact in a knot, GLOMERULUS, with the capsule/tubule (BOWMAN’s capsule) and due to the vessels permeability secrete into the capsule

2) Secretion/Absorption: as the renal tube (connected to the capsule) the capillaries secrete + absorb ions, increasing the renal rubes ionic concentrations

3) Excretion: the fluid travels towards ducts of kidney before being excreted as urine

Question 38

What adaptation of renal tubes assist with diffusion?

Answer 38

It’s elongated and folded to increase SA

Question 39

How do freshwater organisms urine compare to saltwater organisms urine?

Answer 39

Freshwater organisms have a HIGHER OSMOTIC concentration so they have LARGER filtration systems (glomerulus + Bowman’s capsule) to produce dilute urine

dilute urine gets rid of excess water that enters their bodies through osmosis

Question 40

Define Malpighian Tubules: Hint: has to do with the process of urine production

Answer 40

See Doc, 8e:
Blind-ended (one end = solid) tubules
- they connect between the midgut + hindgut

The cells of the tubules actively transport URIC acid, potassium ions and soidum ions from the extracellular fluid in the tubules

A HIGH concentration of solutes in tubules causes water to enter tubules to flush the contents towards the gut

The epithelial cells of the hind gut + rectum actively transport the solutes (NOT uric acid) back into the extracellular fluid

Creating an OSMOTIC gradient which pulls water OUT of rectal contents =creating colloidal suspension (more H2O absorbed)

Uric acid remains in rectum and is excreted as urine

Question 41

What is the structure of nephrons based on? (Hint: 3 things)

Answer 41

1) Class of invertebrates
2) nitrogenous waste they excrete
3) the habitat in which they live

Question 42

Define the Loop of Henle: found in mammals

Answer 42

See Doc, 8f:
- an elongation of the PROXIMAL TUBULE
- functions as a counter-current multiplier that changes concentration gradient of surrounding tissue

main function is to reabsorb water and sodium chloride from urine, which allows the body to produce urine that is more concentrated than blood. This concentration of urine reduces the amount of water needed to survive.

This extends into the medulla region (middle of nephron) of the kidney

Area f this tissue correlates with concentration of urine produced by mamals

Question 43

What kinds of environment is the kidney most efficient in?

Answer 43

Arid environments