Module Two : 4. Organization of Cells

Answer 1

Comparing Different Types of Organisms

Unicellular Organisms
* Composed of single cells.
* Possess cell membranes, cytosol, ribosomes, and genetic material.
* Differentiated by the number of cells, types of cells, and organization.

Colonial Organisms
* Composed of single cells working together.
* Differentiated by the number of cells, types of cells, and organization.

Prokaryotes
* Composed of one prokaryotic cell.
* Have been on Earth for 3.5–4 billion years.
* Limited by lack of organelles and simple structure.
* Unicellular eukaryotic organisms carry out life processes more efficiently than prokaryotes.

Answer 2

Unicellular and Colonial Organisms Overview

Unicellular Organisms
* Directly exposed to the external environment.
* High surface-area-to-volume ratio (SA:V) enables efficient movement of substances and waste removal.
* Examples include Volv ox, coral, and jellyfish.
* Volv ox is a hollow sphere made up of 500 to 60,000 algae cells, each with two flagella and connected by cytoplasm.
* Each cell in the colony has a red ‘eyespot’ that can detect light.
* Eukaryotic choanoflagellates are another example of a colonial organism.

Multicellular Organisms
* Comprises many different types of cells performing specialized functions.
* These specialized cells cannot live independently, unlike unicellular and colonial organisms.
* Processes of obtaining nutrients and getting rid of waste in unicellular and colonial organisms rely on diffusion.
* Multicellular organisms are larger in size, resulting in smaller total SA:V, making passive transport insufficient.
* Functional organization of multicellular organisms overcomes this problem.
* Large organisms are made up of numerous small cells, increasing efficiency of diffusion and osmosis.
* Cells are organized into tissues, allowing for efficient nutrient and gas exchange.
* Different cell types are structurally suited to carry out different functions, increasing their effectiveness.
* Embryonic cells, similar to each other in structure, require protection and nutrients to grow.

Question 3

• Nerve cells
• Loose connective tissue with fibroblasts
• Red blood cells
• Smooth muscleFat (adipose)cells
• Intestinal epithelialcells
• Intestinal epithelialcells
• Striated muscle cells
• Bone tissue with osteocytes
• Embryoniccell

Answer 4

Cell Structure and Specialisation in Organisms

• Cell structure and arrangement in multicellular organisms are closely related to their specific function.
• Specialised cells work together to ensure efficient functioning of the organism.
• Cells differentiate when they become specialized to perform a particular function, developing suitable structural features.
• All specialized cells originate from stem cells, which are undifferentiated and can divide many times over a long period.
• Stem cells can be found in embryos (embryonic stem cells) or adult stem cells, found in various parts of the body, such as the human brain and bone marrow.
• Cell specialisation refers to the particular functions a cell has. Differentiation is the process a stem cell goes through to become specialized.
• Different cells develop as a result of only certain parts of the genetic information being’switched on’.
• Genes that are activated control the types of proteins produced by the cell, determining its particular structure and specialized function.
• Once specialized, differentiated cells lose their capacity to develop into other types of cells or even give rise to the same type of cells.
• In plants, meristematic tissue contains undifferentiated cells, which are differentiated into specialised cells as they continue to divide and mature.

Answer 5

Cell Function and Structure

• Multicellular organisms have many benefits, but specialized cells are incapable of surviving independently.
• Efficient functioning requires well-developed communication and coordination between specialized cells.
• Animals use chemical secretions and nerve cells for efficient message relay.
• Blood cells bind oxygen, provide nutrients, and remove waste.
• Plant cells communicate through chemical and physical contact due to lack of nerve cells and centralised control center.
• Cell structure and specialisation are related to function.
• Cells involved in exchanging substances with the environment have special structural features to increase their Specific Area of Vibration (SA:V).
• Red blood cells transport oxygen around the body in the blood, allowing rapid diffusion of oxygen.
• The absence of a nucleus or organelles in the cell allows more haemoglobin to be carried in the cell.

Answer 6

Structural Organisation of Multicellular Organisms

• Multicellular organisms contain various types of specialized cells, requiring high level of organisation for effective functioning and reproduction.
• Atoms, composed of molecules, form essential chemical substances that form organelles in eukaryotic cells.
• Organelles are specialized for specific functions within the cell, coordinated by the nucleus.
• Specialised cells are collectively organized into tissues, such as heart muscle tissue.
• Organs are grouped together to perform a particular function, such as the heart, which contains muscle tissue, connective tissue, nerve tissue, and epithelial tissue.
• Organ systems, like the cardiovascular system in humans, work cooperatively to ensure the survival of the organism.

Answer 7

Specialised Epithelial Cells and Their Function

Connective Tissue
* Contains an extracellular matrix with cells scattered through it.
* Made up of collagen and elastin protein fibres for strength and flexibility.
* Also contains a substance to fill spaces.
* Types include fibrous connective tissue, loose connective tissue, adipose tissue, cartilage, bone, and blood.
* Examples include adipose tissue, which contains fat storage cells for energy storage, insulation, protection, and cushioning.
* Cartilage, composed of dense collagen fibres, provides strength, flexibility, and cushioning.
* Collagen in skin connective tissue prevents skin from tearing away from the bone.

Nervous Tissue
* Comprises the brain, spinal cord, and peripheral nerves.
* Nerve cells (or neurons) are specialized for communication.
* Neurons consist of multi-branched dendrites and an axon.
* The branching of the dendrites and the long axon of the neuron are specialized for conveying messages.

Muscle Tissue
* Consists of muscle cells called muscle fibres.
* Types include skeletal, cardiac, and smooth muscle.
* Skeletal muscle fibres are voluntary, while cardiac muscle fibres are present in the heart.
* Smooth muscle fibres push substances through specialized organs. Both cardiac and smooth muscle are involuntary.

Plant Cell Organization

Organelles in Plants
* Plant cells are grouped together in tissues to perform a shared function.
* Organs contain different tissues grouped together to carry out a specific function.
* Organ systems contribute to the overall functioning of the organism and ensure each part receives what it needs.

Three Systems of Plant Organs
* Shoot System: Supports the plant, enables transport of substances, exchanges gases, and carries out photosynthesis and reproduction.
* Root System: Absorbs water and nutrients from the soil for the rest of the plant.
* Vascular System: Made up of xylem and phloem vessels.

Types of Plant Tissues
* Meristematic Tissue: Found at the tips of roots and shoots.
* Dermal Tissue: Protects plant tissues and controls interactions with the plant’s surroundings.
* Vascular Tissue: Responsible for the transport of substances around the plant.
* Ground Tissue: Comprises all internal cells of a plant other than the vascular tissue.