IQ2 - Module 2: Organisation of Living Things

Question 1

What are nutrient and gas requirements?

Answer 1

Autotrophs and heterotrophs have a fundamental difference in their functioning that is reflected in the different methods used to obtain their nutrient and gas requirements. These are required to maintain efficient and effective metabolic function.

Question 2

what are autotrophs

Answer 2

Autotrophs are able to make their own food by using energy to convert inorganic compounds into organic compounds. This process is called carbon fixation

Question 3

what are autotroph gas requirements?

Answer 3

▪ Carbon dioxide
− moves into the plant for photosynthesis
▪ Oxygen
− moves into the plant for cellular respiration

Question 4

what are autotroph nutrient requirements?

Answer 4

▪ Water
− moves into the plant for photosynthesis and osmoregulation in cells
▪ Glucose
− produced by photosynthesis
− utilised for cellular respiration
▪ Mineral ions
− moves into the plant
▪ Proteins & Lipids
− produced from glucose and mineral ions

Question 5

what do photoautrophs (photosynthetic) do?

Answer 5

▪ obtain energy source from carbon fixation from solar energy
▪ obtain carbon source from carbon dioxide
▪ most autotrophs
▪ e.g. green plants, phytoplankton

Question 6

what do chemoautotroph (chemosynthetic) do?

Answer 6

▪ obtain energy source from carbon fixation by chemical reactions of inorganic molecules
▪ obtain carbon source from carbon dioxide
▪ live in extreme environments
▪ e.g. archaea, nitrifying bacteria, methanogens

Question 7

what are heterotrophs?

Answer 7

Heterotrophs must obtain organic compounds from eating other organisms, as they can not carry out carbon fixation.
Organic substances that are ingested are broken down in the body and then reconfigured into the substances that are needed.

Question 8

what are heterotrophs gas requirements?

Answer 8

▪ Carbon dioxide
− not required as it moves out of the animal
▪ Oxygen
− moves into the animal for cellular respiration

Question 9

what are heterotrophs nutrient requirements?

Answer 9

▪ Water
− consumed from food
− moves into the animal for osmoregulation in cells
▪ Glucose
− consumed from food
− moves into the animal for cellular respiration
▪ Mineral ions
− consumed from food
▪ Proteins & Lipids
− consumed from food

Question 10

what is a photoheterotroph?

Answer 10

▪ obtain energy source from solar energy
▪ obtain carbon source by consuming organic compounds
▪ e.g. heliobacteria, green non-sulfur bacteria

Question 11

what is a chemoheterotroph?

Answer 11

▪ obtain energy source from organic compounds using cellular respiration
▪ obtain carbon source by consuming organic compounds
▪ e.g. animals, fungi, some bacteria

Question 12

what are plants nutrient requirements?

Answer 12

Plants obtain their nutrients from the soil and through the process of photosynthesis. Water and minerals are obtained from the soil and photosynthesis produces glucose, which can then be used to produce other nutrients.

Question 13

what do roots have and how can this be achieved?

Answer 13

Roots have a very large surface area due to the extension of root hairs to efficiently absorb water and inorganic minerals from the soil.

This can be achieved by:
▪ branching of root systems
▪ root hair zone (epidermal cells have extensions called root hairs)
▪ flattened epidermal cells

Question 14

what is the movement into roots?

Answer 14

▪ water moves in by the process of osmosis
▪ mineral ions move in by the process of diffusion (facilitated diffusion or active transport may be involved)
▪ O2 diffuses in
▪ CO2 diffuses out

Question 15

what is a leaves structure?

Answer 15

The thin, flat and broad structure of leaves are adapted to absorb maximum sunlight by chlorophyll as it provides a large surface area for photosynthesis.

This means that no internal cells are too far from the surface to receive light. The epidermis layer is transparent allowing the sun to penetrate through to the photosynthetic cells beneath. The cells that occur in the mesophyll are responsible for most of the plant’s photosynthesis.

Question 16

what are the two main types of mesophyll?

Answer 16

▪ Palisade cells – elongated that are dense with chloroplasts and the main
photosynthetic cells in leaves. They are situated vertically, immediately below the upper epidermis, so they exposed to the maximum amount of sunlight. The large number of chloroplasts in these cells ensures
a maximum rate of photosynthesis.

Spongy cells – second most important photosynthetic cells, situated between the palisade cells and the lower epidermis. They have fewer chloroplasts than the palisade cells and are irregular in their shape and distribution.

Question 17

what are the number of factors that affect the rate of photosynthesis?

Answer 17

There a number of factors that affect the rate of photosynthesis.
▪ CO2 – levels in the air remain relatively constant, therefore the
controlling factor is if the stomata are open or closed, meaning less CO2 limits the rate of photosynthesis

Water – amount needed is small, meaning there will be a sufficient amount for photosynthesis and if water availability is low, the stomata close to conserve water
▪ Light – varies in the natural environment over the course of the day, at some point, no matter the light intensity, the rate will be constant because the chloroplasts are working at maximum rate

Question 18

what are plants gas requirements?

Answer 18

Plants have many specialised structures that allow them to efficiently exchange gases with their environment. This allows oxygen and carbon dioxide to move in and out.

The structure of leaves is well adapted for gaseous exchange as they:
▪ are large and usually flat, maximising surface area
▪ the surfaces of these cells are moist so that gases are dissolved, allowing
for more effective movement
▪ most gaseous exchange in plants occurs through the stomata and lenticels

contain open air spaces formed by the irregular shape and arrangement of the spongy mesophyll tissue providing even greater surface area and allows the gases and water to move freely through much of the leaf without having to pass through cells

Question 19

what is the stomata?

Answer 19

Stomata are pores mostly found in the lower epidermis of a leaf which open to an air space within the mesophyll. The upper epidermis may have a few, however the waxy cuticle of leaves is non-porous to both water and gas.
They play an important role in regulating the exchange of gases and water between the internal and external environment.

Question 20

what does a stomata consist of?

Answer 20

Each stomata consists of two highly specialised epidermal cells called guard cells. The guard cells surround the pore to control the ability of stomata to open and close.

▪ Guard cells fill with water (turgid), they bend outwards and open the stomata allowing for the exchange of gases and water
▪ Guard cells lose water (flaccid), they straighten and close the stomata, preventing the exchange of gases and water
Plants need to balance their gaseous requirements while minimising water loss

Question 21

what are the number of factors that affect the opening and closing of the stomata?

Answer 21

▪ Light – main factor as they open during the day and close at night
▪ Temperature – an increase lead to more water vapour to be lost through
open stomata causing guard cells to lose water closing the stomata

Water – a decrease may limit photosynthesis causing the concentration of CO2 to rise, causing the stomata to close. If the internal concentration of CO2 falls, the stomata will open. If the air is saturated with water vapour, the rate of water evaporation will decrease, enabling the stomata to remain open

Question 22

what is lenticels?

Answer 22

Lenticels are pores on the woody parts of the plant (trunks and branches). The exchange of gases and water occurs slowly.

Question 23

what is the animals gas requirements?

Answer 23

Animals have many specialised structures that allow them to efficiently exchange gases between the internal and external environment. This occurs by diffusion across cell membranes.

Oxygen is essential for all cells to carry out cellular respiration to release energy from the nutrients they have consumed. As a result carbon dioxide is produced and must be removed, as it is toxic if its concentration is too high, decreasing the pH of cells.

The respiratory system enables the exchange of gases between an organism and its environment.
It contains organs made up of specialised tissues that allow an organism to take in oxygen and to remove carbon dioxide from its body.

Question 24

what do different animals possess?

Answer 24

Different animals possess different respiratory organs depending on their environment. Although, all gas exchange structures share common characteristics to ensure efficient functioning and maximum exchange.
They all have a:
▪ large surface area (enhanced folding, branching or flattening to allow faster rate of diffusion)

▪ moist, thin surface (thinness decreases distance gases have to travel and easier to dissolve for diffusion)
▪ close proximity to an efficient transport system (transport the gases to and from all cells)
▪ greater concentration of required gas on one side of the membrane (concentration gradient is maintained)

Question 25

air passes through what respiratory structures in mammals?

Answer 25

Mammals
Air passes through the following respiratory structures:
▪ nasal cavity
▪ pharynx
▪ trachea
▪ bronchi
▪ bronchioles
▪ alveoli

Question 26

what is the alveoli?

Answer 26

The respiratory system of terrestrial animals are internal to reduce the loss of water from the respiratory surface. The gaseous exchange surfaces in mammals are located in lungs and these structures are known as alveoli.

Question 27

what are capillaries?

Answer 27

Each thin-walled alveolus is composed of an air sac that is connected to the external environment and is surrounded by tiny thin-walled blood vessels called capillaries.

Question 28

what features does the alveoli have which is efficient for gas exchange?

Answer 28

Alveoli in the lungs have all the features for efficient gas exchange:
▪ increased surface area – folding of the interior lining
▪ thin lining made of flattened cells that are in a single layer – facilitating the efficient diffusion of gases across a small distance
▪ moist surface – enhance the efficiency of diffusion
▪ numerous blood capillaries – closely surround each alveolus to ensure they are in close contact with the blood

Question 29

how does the movement of gases between air in the alveoli answer bloodstream occur?

Answer 29

The movement of gases between air in the alveoli and bloodstream occurs by diffusion across a concentration gradient.
▪ oxygen is more concentrated in the alveoli than the capillaries, so diffuse from the air sacs into the bloodstream
▪ carbon dioxide is more concentrated in the capillaries than the alveoli, so diffuse from the bloodstream into the air sacs

Question 30

what is the gas exchange that occurs within fish?

Answer 30

The gas exchange structures within fish are known as gills.

Question 31

what do insects take in and expel through structures through?

Answer 31

Insects take in and expel air through structures called spiracles, which are in effect breathing pores.

Question 32

what are animals nutrient requirements?

Answer 32

Animals need to take in (eat) all of their nutrients to supply energy and provide the building blocks for organic compounds.

The digestive system enables the breakdown of large and complex molecules into smaller and simpler molecules that can be absorbed into the bloodstream.

Question 33

what are animals nutrient requirements?

Answer 33

Animals need to take in (eat) all of their nutrients to supply energy and provide the building blocks for organic compounds.

The digestive system enables the breakdown of large and complex molecules into smaller and simpler molecules that can be absorbed into the bloodstream.

Question 34

what is digestion and the two types of digestion?

Answer 34

Digestion is the breaking down of large, complex molecules into smaller, simpler molecules.
The 2 types of digestion are mechanical (physical) and chemical.

Question 35

what is mechanical digestion?

Answer 35

The physical breakdown of food into smaller pieces to increase the surface area for the action of enzymes. For example:
▪ begins in the mouth when the different types of teeth break food into smaller pieces by cutting, tearing, chewing and grinding.
▪ the churning motion of the stomach continues the process of mechanical digestion

Question 36

what is the chemical digestion?

Answer 36

Digestive enzymes enable the chemical breakdown of large, complex molecules into smaller, simpler molecules that can be absorbed into the transport systems of the body.
Some of the simpler substances obtained are:
▪ glucose from complex carbohydrates
▪ amino acids from proteins
▪ glycerol and fatty acids from lipids
▪ nucleotides from nucleic acids

Question 37

different organs of the digestive system are specialises to perform different functions to achieve digestion of food. what is the mouths function?

Answer 37

Mouth
▪ Mechanical digestion
− teeth break the food up into smaller pieces with greater surface area for the more efficient action of enzymes
▪ Chemical digestion
− amylase enzyme, in saliva, breaks down the complex carbohydrate starch into the simpler sugar maltose

Once the food has been chewed into small pieces and mixed with saliva, the tongue forms it into a ball shape called the bolus. This is then swallowed and enters the oesophagus.

Question 38

what is the oesophagus function in digestion?

Answer 38

Once the bolus enters the oesophagus, it travels along the soft-walled, muscle-ringed tube to the stomach.
▪ Mechanical digestion
− muscular contractions move the bolus
by peristalsis
▪ Chemical digestion
− digestion of starch continues

Question 39

what is the stomachs function in digestion?

Answer 39

Circular sphincter muscles control the movement of substances into and out of the stomach.
▪ Mechanical digestion
− continues due to the relaxation and contraction of the stomach walls

Question 40

what is the stomachs chemical
digestions function?

Answer 40

− gastric juices, secreted from the wall of the stomach, contains HCl and
digestive enzymes that combine with the bolus to form chyme
− pepsinogen enzyme is converted into an active form called pepsin in the acidic environment and begins to breakdown protein into shorter chain peptides

Question 41

what is the small intestines function?

Answer 41

The chyme from the stomach enters the small intestine.
The highly folded small intestine is approximately 7m long in an adult and contains 3 main regions:
▪ Duodenum ▪ Jejunum
▪ Ileum

Question 42

what is the duodenums function?

Answer 42

As the chyme enters the duodenum, it stimulates the release of pancreatic juices into the area.
▪ Mechanical digestion
− bile (produced by the liver and stored in the gall bladder) is released into the duodenum to break down (emulsifies) the fats into small pieces or fat droplets
▪ Chemical digestion
− amylase and trypsin continue the breakdown of carbohydrates and proteins
− lipase breaks down lipids into fatty acids and glycerol

Question 43

what does the pancreas do?

Answer 43

Pancreatic juices are secreted by the pancreas into the duodenum.
They contain a mixture of the digestive enzymes amylase, trypsin and lipase, as well as bicarbonate ions. The bicarbonate ions act to neutralise the acidic chyme leaving the stomach.
Also, produces the hormones insulin and glucagon to regulate sugar levels in the blood.

Question 44

what is absorption in the digestive tract?

Answer 44

The absorption of substances mostly occurs in the jejunum section of the small intestine.
The internal surface area is increased by millions of tiny projections (tiny folds) called villi. Villi walls are moist and one cell thick, which allows the rapid transfer of nutrients by diffusion or active transport to the many blood and lymphatic vessels beneath the surface to transport these nutrients to the body tissues.

Glucose and amino acids are absorbed into the capillaries, while fatty acids and glycerol move into the lacteal. Some water absorption will also occur here.
Lacteals are vessels of the lymphatic system (another transport system).

Question 45

what is the livers function?

Answer 45

Digested food, once absorbed into the bloodstream, travels to the liver, which is the centre of food metabolism.
It plays an important role in keeping sugars, glycogen and protein levels in balance in the body. It also detoxifies the blood.

Question 46

what is the large intestines function?

Answer 46

When all of the required digestive products have been absorbed in the small intestine, the remaining undigested material moves to the large intestine.
This material is composed of substances such water, salts and dietary fibre.
The large intestine has 2 main sections: ▪ Colon
▪ Rectum

Question 47

Colon and Rectum function

Answer 47

In the colon the water and some salts are absorbed back into the bloodstream, with the undigested material compacting into a more solid substance.
The remaining waste material, known as faeces, is moved into the rectum by peristalsis and then eliminated from the body through the anus.