Patterns In Nature 3

Question 0

What is a young cell called?

Answer 0

An embryonic cell. This type of cel can only divide and give rise to new cells. They can become specialised and differentiated when they mature.

Question 1

Identify some examples that demonstrate the structural and functional relationship between cells, tissues, organs and organ systems in multicellular organisms.

Answer 1

Cells
- flattened e.g. tissue lining the air sacs in lungs
- elongnate e.g. photosynthetic cells in leaves
to create a create a greater surface area to volume ratio.
- exposed edges of cells may have folds e.g. root hair cells that absorb water and minerals for plants

A group of cells that is similar in structure and works together to carry a common purpose is called a tissue.

Likewise, a group of tissues that have a common function are called an organ. And organ is an arrangement of different types of tissues e.g. a leaf is an organ as much as a heart in an animal is.

Furthermore, a group of organs is called a system. These organs all work together to achieve an overall body function e.g. digestive system.

A multicellular organism is composed of several systems.

Question 2

What is a specialised cell and what is it called?

Answer 2

If a cell becomes specialised, it is differentiated. These mature cells are structurally different from other cells. Once cells have become specialised and form a particular type of issue, differentiated cells lose their capacity to develop into other types of cells. They may not even be able to divide.

Question 3

What are stem cells?

Answer 3

Undifferentiated cells that are able to divide and differentiate into other types of cells.

Question 4

Distinguish between autotrophs and heterotrophs in terms of nutrient requirements.

Answer 4

Autotrophs absorb inorganic nutrients but can manufacture their own organic nutrients via photosynthesis or chemosynthesis.

Heterotrophs, however, rely on outside sources to feed on for both organic and inorganic nutrients.

Question 5

What are the test chemicals and their colours for glucose, starch and protein?

Answer 5

Glucose - Benedict’s solution - yellow or orange
Starch - Iodine solution - dark blue or black
Protein - Biuret - purple

Question 6

What are the requirements for photosynthesis and its role in ecosystems?

Answer 6

• Carbon dioxide
• Water
• Chlorophyll
• Sunlight

Through photosynthesis, carbon dioxide is replaced with oxygen. This is vital for all living things as oxygen is a necessary requirement for respiration to create energy (ATP).

Photosynthesis is also the only main process that creates chemical energy - this starts off all food chains in every ecosystem.

Question 7

What is the word equation for photosynthesis?

Answer 7

Carbon dioxide + water (through chlorophyll and sunlight) Oxygen + glucose + water

This is a summary of a chain of biochemical reactions.

Question 8

Explain the relationship between the organisation of structures used to obtain water and minerals in a range of plants and the need to increase surface area available for absorption.

Answer 8

Roots are responsible for absorbing water and other inorganic substances.

A large surface area is needed for efficient absorption - the greater the surface to area ratio, the more rapid the reaction. Osmosis is a slow process, and since plants need a high uptake of water to function, a large surface area is needed.

The outer layer of plant organs is the epidermis. This is where, in the root, water and minerals are absorbed.

Water is absorbed through osmosis. Minerals are absorbed via diffusion and, when necessary, facilitated diffusion and active transport.

Surface area is increased by root hairs (12x) and extensive branching of root system (tap root, fibrous or adventitious).

Water and minerals enter through epidermal cells then move to xylem to the cortex, then another xylem to the rest of the plant.

Question 9

Explain the relationship between the shape of leaves, the distribution of tissues in them and their role.

Answer 9

Leaves need to

• conduct photosynthesis
• release oxygen
• produce glucose and transport it to other areas of the plant
• conduct transpiration

Structure of leaves:

• large surface area for efficient aborption
• pores in the leaves’ surface to exchange gases
• cells that contain chloroplasts and chlorophyll to trap light energy
• water and food transport system throughout entire plant

Leaves are thin so that the SA:V is large and that no cell is not exposed to sunlight.
The epidermis is transparent for the same reason. This layer is also able to secrete a water-proof cuticle to prevent excessive water loss. Stomata control the exchange of gases and water and are usually more numerous on the underside of the leaf.

The mesophyll, or middle of the leaf is made of palisade and spongy cells.
The palisades are located on top, elongated and contain chloroplasts.
The spongy cells are filled with air spaces, irregular in shape and deal with gaseous exchange.

Xylem transports water and inorganic substances; phloem transports sugars produced by photosynthesis.