M2

Question 1

Identify what is meant by the terms differentiation and specialisation

Answer 1

Cell differentiation is the process by which cells become specialized in order to perform different functions. Specialised cells are formed from the differentiation of stem cells. Examples of specialised cells include red blood cells that carry oxygen around the body.

Question 2

Explain why multicellular organisms have a hierarchy of organisation

Answer 2

Most multicellular organisms have a hierarchy of organisation: each part works together to form the next, more complex part:

Cells → Tissues → Organs → Organ systems → Organisms
For example:
Lung cells → Lung tissue → Lungs → Respiratory systems → Humans
Atoms: Atoms are the simplest level.
Molecule: Two or more atoms comprise a molecule.
Cell: A cell is the smallest unit that can carry out all the processes of life.
Tissue: A group of similar cells that carry out a specific function.
Organ: Groups of tissues functioning as a unit, performing the same function.
Organ System: A group of organs that work together to carry out related tasks. Various organ systems work together to form a multicellular organism.

Because multicellular organisms are complex, different cells carry out specialised functions, and work together to form more complex structures. These systems ensure that all cells, irrespective of type or location, are able to access cell needs, such as oxygen and nutrients, as well as get rid of wastes. The more complex the organism, the more specialised cell types as well as the need to have transport systems.

Question 3

Define the terms:
-unicellular
- colonial
- multicellular

Answer 3

unicellular –> only one cell that carries out every function, bacteria, protists and yeast
Multicellular –> composed of multiple cells independent to varying degrees, humans, animals
colonial –> individual cells living in close association with each other, eg. coral colonies

Question 4

Observe longitudinal and cross-section LM images of xylem and phloem

Question 5

Describe the structure and function of microscopic structures, in plants (xylem)

Answer 5

Xylem consists of dead cells. The cells that make up the xylem are adapted to their function: They lose their end walls so the xylem forms a continuous, hollow tube. They become strengthened by a substance called lignin. Xylem tissue transports water and nutrients from the roots to different parts of the plant

Question 6

Describe the structure and function of microscopic structures, in plants (phloem)

Answer 6

Made of living cells that are supported by companion cells. Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes that allow sugars and amino acids to be transported via translocation

Question 7

Describe the structure and function of macroscopic structures in plants (leaf)

Answer 7

Cuticle, thin waxy waterproof layer –> protects the inner cells, prevents water loss and allows sunlight to penetrate for photosynthesis

upper/lower epidermis, transparent and usually thin –> protects the inner cells, prevents water loss and allows sunlight to penetrate for photosynthesis

epidermis/cuticle, contains guard cells surrounding stomata –> regulaetes gas exchange and water loss. The waxy cutivle protects the leaf from excess water loss and the opening and closing of the stomata controls the amount of gas and water vapour entering and exiting the leaf

palisade mesophyll, tightly packed column shaped cells with many chloroplasts, close to upper epidermis –> photosynthesis

spongy mesophyll, loosely packed, rounded cells with fewer chloroplasts with air spaces around the cell –> gas exchange, including the diffusion of carbon dioxide throughout the leaf

xylem/phloem, tubular vessels –> transport of fluids

Question 8

Describe the structure and function of macroscopic structures in plants (root)

Answer 8

Root systems are used to anchor the plant to soil for support. the exterior of the root is the epidermis, composed of epidermal cells. Some of these epidermal cells have long, fine extensions called root hairs, which increase surface area and absorb water and dissolved mineral ions from the soil.
The next layer of a root is the cortex. The cortex is composed of parenchyma cells, which can store nutrients and starch.
The innermost central region of the root contains the vascular tissue: xylem and phloem.

Question 9

Describe the structure and function of macroscopic structures in plants (stem)

Answer 9

The stem is covered by the epidermis, which is the dermal tissue. Like the epidermis in humans, it provides a protective barrier, as well as reducing water loss. Inside the epidermis, and surrounding the vascular tissues is the ground tissue. The ground tissue allows storage of carbohydrates, as well as strengthening the stem

Question 10

Describe the function of the different tissues in leaves (dermal)

Answer 10

Dermal tissue is the outer layer of tissue surrounding the entire plant, which covers and protects the plant, and controls gas exchange and water absorption.

Question 11

Recall the differences between autotrophs and heterotrophs

Answer 11

Autotrophs are organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis). Heterotrophs cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition.

Question 12

Recall the locations of photosynthesis and cellular respiration

Answer 12

PS: In all autotrophic eukaryotes, photosynthesis takes place inside an organelle called a chloroplast. In plants, chloroplast-containing cells exist in the mesophyll. Chloroplasts have a double (inner and outer) membrane.

CR: Cellular respiration takes place in the cytoplasm and mitochondria of each cell of the body. Glycolysis is one of the main processes involved in cellular respiration. Glycolysis is the pathway that converts sugar into energy, or glucose (C6H12O6) into pyruvate (CH3COCOO), generating ATP during the conversion

Question 13

Describe how scientists’ understanding of photosynthesis developed over time

Question 14

Explain what is meant by transpiration-cohesion-tension theory, and explain the evidence that supports this theory

Answer 14

The cohesion-tension theory is a theory of intermolecular attraction that explains the process of water flow upwards (against the force of gravity) through the xylem of plants. Transpiration pull, utilizing capillary action and the inherent surface tension of water, is the primary mechanism of water movement in plants. (need to identify a diagram in depth)

Evidence to support transpiration -cohesion-tension:

If a trunk or stem is damaged and a xylem cell is broken water does not leak out (which it would if the vessels were under pressure). Once air enters the tree can no longer draw up water because the continuous column of water has been broken.
The trunks of trees reduce in diameter during the daytime when transpiration is at its greatest (increased photosynthesis and temperature). This is because adhesion of water molecules to walls of xylem results in a tension which pulls the xylem walls in. At night when transpiration is at its lowest there is less tension so the diameter increases.

Question 15

Perform an experiment to investigate transpiration in plants

Question 16

Give examples of the use of radioisotopes to investigate plant structure and photosynthesis

Answer 16

the radiation emitted from isotopes of elements can be detected by photographic paper or special instruments such as the“Geiger counter”. For example, heavy elements such as zinc are transported faster than magnesium and therefore have a higher distribution within a plant. If a radio-isotope is introduced into a plant or animal, its transport through the body can be followed by monitoring the radiation the isotope emits. This “tracer” technique is one of the more important methods used to study the movement of substances in living things

Question 17

Describe the structure and function of stomata and guard cells

Answer 17

Within the lower epidermis are the stomata. The stomata regulate the exchange of carbon dioxide, oxygen and water vapour between a plant’s internal and external environment.

Question 18

Recall the meaning of gaseous exchange

Answer 18

The diffusion of gases from an area of higher concentration to an area of lower concentration, especially the exchange of oxygen and carbon dioxide between an organism and its environment.

Question 19

Describe the properties of efficient exchange

Answer 19

The gaseous exchange surface must have a large surface area in contact with the environment, whether directly or via a transport system.
The gaseous exchange surface must be moist, because the gases must dissolve in water before passing through the membrane by diffusion. For this reason, gaseous exchange is different in terrestrial and aquatic organisms.
The membrane must be in close contact with the blood supply (or other transport system) to carry gases between cells from the organs where the gaseous exchange membranes are located.

Question 20

Describe the properties of respiratory systems in a range of animals (humans)

Answer 20

The gaseous exchange surface must have a large surface area in contact with the environment, whether directly or via a transport system.
The gaseous exchange surface must be moist because the gases must dissolve in water before passing through the membrane by diffusion. For this reason, gaseous exchange is different in terrestrial and aquatic organisms.
The membrane must be in close contact with the blood supply (or other transport system) to carry gases between cells from the organs where the gaseous exchange membranes are located.

Question 21

Describe the properties of respiratory systems in a range of animals (fish)

Answer 21

Aquatic organisms do not need to internalise gaseous exchange membranes, as there is no chance of them drying out. Hence, they are exposed directly to the environment in the form of gills. Gills are thin and highly folded, increasing their surface area. Water enters a fish’s mouth and passes over the gills. When most fish are stationary they gulp water to maintain the flow over the gills; they swim with their mouths open to maintain the flow of water. Gaseous exchange occurs on the gill surface, which, similarly to alveoli, are covered in capillaries that increase the rate of diffusion. All of this helps aquatic animals to compensate for the fact that the concentration of oxygen is much lower in water than air.

Question 22

Describe the properties of respiratory systems in a range of animals (frogs)

Answer 22

Frogs have a number of different ways that they can perform gaseous exchange. When they are at rest, gaseous exchange occurs via membranes in their mouth. When underwater, gaseous exchange occurs through the skin. Frogs can also breathe through nostrils. Frogs’ lungs are much simpler than those of mammals, and gaseous exchange is less efficient. The large number helps compensate for this, as does the fact that, as ectothermic organisms, frogs don’t need to devote any of the energy from cellular respiration to maintaining their body temperature, hence oxygen requirements are lower.

Question 23

Describe the properties of respiratory systems in a range of animals (insects)

Answer 23

Insects don’t have lungs or capillaries. Gaseous exchange takes place through the sides of their bodies through a series of pores called spiracles, which are controlled by valves to minimise water loss. Each spiracle allows air to move into a network of tracheal tubes which infiltrate their whole body. The tracheal tubes then form branched structures called tracheoles, which increase surface area. From the tracheoles, the gases diffuse directly in and out of cells.

This method of gaseous exchange limits the size of insects- if they were larger, the SA:V ratio would mean that exchange would not be efficient enough to meet the needs of the organism.

Question 24

Examine a range of microscopic structures (alveoli in mammals)

Answer 24

The alveoli are the location of gaseous exchange. The alveoli fit the criteria for efficient gas exchange listed above. They have a very large surface area, increasing the rate of diffusion. Alveolar epithelial cells are elongated, very thin and arranged in a single layer which increases the rate of diffusion, as does the large number of capillaries that surround the alveoli. Finally, they are internalised, in the moist environment of the lungs, ensuring that water loss is minimised.

Question 25

what is the practical/method for investigating lung capacity

Question 26

Compare physical and chemical digestion

Answer 26

In physical digestion, your body mechanically breaks down food, grinding or smashing it into smaller pieces. However, during chemical digestion, enzymes, or tiny proteins, alter the structure of the food, which is made up of lots of atoms linked together.

Question 27

Describe the location of nutrient absorption and breakdown in humans, and waste elimination

Answer 27

In humans, nutrient absorption and breakdown take occur primarily in the small intestine, where enzymes break down food into absorbable molecules. The small intestine’s lining contains villi and microvilli that facilitate nutrient absorption through the bloodstream. The large intestine absorbs water and electrolytes from indigestible substancesm which form feces that are stored in the rectum until excretion through the anus.

Question 28

Examine the digestion of food in other organisms (carnivores/herbivores)

Answer 28

Herbivores have to take in a large amount of food that requires complex digestion, thus they have large specialised digestive systems. Most herbivores have several stomach chambers. They also have a comparatively longer digestive tract than carnivores. Carnivores take in a smaller amount of high energy food and have smaller and less complex digestive systems.

Question 29

Construct a table to summarise the similarities and differences in nutrient and gas requirements of autotrophs and heterotrophs

Answer 29

Nutrient/gas requirements – autotroph –heterotroph

oxygen gas –> diffuses ito the plant across cell surfaces –> diffuses through respiratory surfaces

carbon dioxide –> diffuses into the plant –> not required

water –> diffuses into the roots –> ingested into the digestive system

glucose –> produced by photosynthesis –> ingested into digestive system as either simple or complex carbohydrates, and absorbed into the bloodstream

proteins, lipids –> produced by plant from glucose and ions –> ingested and absorbed into the bloodstream as amino acids, fats and glycerol

Mineral Ions –> move into plant through roots by diffusion and active transport –> ingested and absorbed into bloodstream

Question 30

Explain the process by which water is transported around plants using transpiration-cohesion tension theory

Answer 30

1) water evaporates from the mesophyll due to heat from the sun (transpiration), this leaves the cells with a negative water potential which cusases more water to diffuse in through osmosis.

2) this increase in water tension pulls more water into the leaf. this is known as tranpiration pull

3) water molecules are cohesive due to the fact they form hydrogen bonds. This is known as cohesion so when some are pulled into the leaf others follow. This pulls the whole column of water in the xylem up from the roots to mesophyll tissue in the leaves

4) water enters the stem through the roots and the cycle repeats.

Question 31

Explain the process by which substances are transported around the plant via translocation

Answer 31

Translocation occurs in the phloem tissue, which consists of tube-like structures called phloem vessels. These phloem vessels run from the leaves into every other part of the plant and are responsible for transporting dissolved organic solutes, such as sucrose and amino acids, from the sources to the sinks.

Question 32

Compare open and closed circulatory systems

Answer 32

Some simple animals, such as insects, have open circulatory systems. They possess a heart, but lack blood vessels. Instead, haemolymph flows around all cells, which is the open circulatory system equivalent of blood in closed circulatory systems. Materials are able to diffuse directly from the haemolymph into cells. The haemolymph is pumped by a heart, but some insects also use body movements to accelerate the process.

Vertebrates such as fish, birds and mammals all have closed circulatory systems. A heart pumps the blood around the body in sealed blood vessels. Pulmonary circulation transports blood between the heart and lungs; systemic circulation moves blood from the heart to the rest of the body.

A closed circulatory system is more efficient than an open circulatory due to the following reasons: As blood flows inside the blood vessels, it circulates with more pressure reaching far distances. Blood circulates faster in a closed system, thus transporting more oxygen, nutrients, and wastes to the body cells.

Question 33

Describe the key components of the mammalian circulatory system

Answer 33

The mammalian circulatory system is divided into three circuits: the systemic circuit, the pulmonary circuit, and the coronary circuit.

Blood enters the right atrium through an upper, superior vena cava and a lower, inferior vena cava. From the right atrium, blood flows through the funnel-shaped tricuspid valve into the pulmonary artery. Blood re-enters the heart through the mitral valve, into the right ventricle. Blood then travels up through the aortic valve, into the aorta.

Question 34

Relate artery and vein structure to function

Answer 34

Arteries: blood vessels that transport blood from the heart. This is oxygenated blood. Because they transport blood away from the heart, they have thick muscular walls to withstand the force from the high pressure needed to pump the blood all around the body. Arterioles, or branches of the arteries, connect them to capillaries.

Veins: transport the deoxygenated blood from organs back to the heart. They have the same structure as arteries but the muscle wall is thinner and veins have a larger diameter than arteries. Because they have thinner walls, and lower pressure, they often rely on valves that prevent blood from flowing in the wrong direction. Venules are the vein branches that connect to capillaries.

Question 35

Describe features of the lymphatic system

Answer 35

find interactive for this (maybe link?)

Question 36

State how the composition of blood changes as it moves around the body (dissolved gases)

Answer 36

Oxygen diffuses into the bloodstream from the alveoli, to be transported to all the cells of the body. Similarly, carbon dioxide diffuses from the bloodstream into the alveoli, to follow the reverse path to be exhaled.

Question 37

State how the composition of blood changes as it moves around the body (glucose)

Question 38

State how the composition of blood changes as it moves around the body (amino acids)

Question 39

Specialised cells in animals (blood)

Answer 39

Red blood cells are adapted for the transport of oxygen. They are small and flexible so they can fit through narrow vessels, have a bi-concave shape that maximises their surface area to absorb oxygen, have a thin membrane so gases easily diffuse through, and contain haemoglobin which binds to oxygen.

Question 40

specialised cells in animals (nerve cells)

Answer 40

Specialized projections called axons allow neurons to transmit electrical and chemical signals to other cells. Neurons can also receive these signals via rootlike extensions known as dendrites

Question 41

Describe the function of the different tissues in leaves (vascular)

Answer 41

Vascular tissue transports water, minerals, and sugars to different parts of the plant. Vascular tissue is made of two specialized conducting tissues: xylem, which transports water and also provides structural support, and phloem, which transports sugars from sites of photosynthesis to other parts of the plant.

Question 42

Describe the function of the different tissues in leaves (ground)

Answer 42

Ground tissue carries out different functions based on the cell type and location in the plant, including photosynthesis, structural support for the stem and the vascular tissue, and storage for water and sugars.

Question 43

Examine a range of microscopic structures (alveoli in mammals)

Answer 43

In vascular plants (ferns, gymnosperms and flowering plants) chloroplasts are located in the mesophyll cells in the leaves and in the stem. In non-vascular plants (mosses and worts) chloroplasts are in the leaves.