Biology Module 2 - Organisation of Living Things

Different Organisms

Organisms can exist as a:

• Single cell (unicellular)

• Single cells working together (colonial)

• Organism made up of many cells (multicellular)

Similarities of these different types of organisms include:

• They are all composed of cells

• These cells all possess cell membranes, cytosol, ribosomes and some sort of genetic material

Differences occur in:

• The number of cells present in the organism

• The type of cells

• The organisation of the cell

Unicellular

• Contain one cell that can be either prokaryotic or eukaryotic

• A single cell is responsible for all of its life processes

• Unicellular eukaryotic organisms can carry out all the necessary life processes in a more efficient manner than the prokaryotes by the means of specialised organelles

• Unicellular organisms are always directly exposed to the external environment.

Colonial Organisms

• Made up of a group of identical single-celled organisms

• All individuals in the colony are capable of carrying out each function necessary for life

• Some colonial organisms contain cells that have specialised functions that are coordinated with other cells in the colony

• E.g. jellyfish and coral

Multicellular Organisms

• Made up of many different types of cells

• Similar cells are grouped together and perform specialised functions that combine together for the efficient functioning of the organism

• The specialised cells in multicellular organisms cannot live independently

Specialised Cells

• Differentiate → when cells become specialised to perform a particular function

• They develop suitable structural features that allow them to carry out their specific functions

• All specialised cells originate from cells that are known as stem cells

• These stem cells are undifferentiated and are able to divide many times and become specialised

• Cell specialisation → specific functions a cell has

• Differentiation → the process that a stem cell goes through to become specialised

• Once a cell has become specialised it loses its ability to develop into other types of cells

Cells working together

• Specialised cells in multicellular organisms are reliant upon the other cells to carry out the functions that they cannot

• There is a requirement for well-developed communication and coordination between the many specialised cells

Cell Organisation, Specialisation and Functioning

Animal Cells

• The different specialised cells found in complex animals are components of the 4 general types of tissues found in animals → epithelial, connective, nervous, muscle

Epithelial Tissue

• A tissue that covers body surfaces, protects organs and forms glands

• The cells in this tissue are densely packed and can occur in either single sheets or layers, depending on their location and function

• It doesn’t contain blood vessels and relies on the underlying connective tissue for nutrients

• The cells are organised very close together to aid their role as barriers to injury and infection

Connective Tissue

• Varies greatly in both form and function

• ALL connective tissue share the common characteristics of an extracellular matrix with cells scattered through it

• This matrix is made up of the protein fibres collagen (strength) and elastic (flexibility) and another substance to fill the spaces

• It provides support, ensures that different parts of the body are bound together and protects against damage

Nervous Tissue

• Nervous system → brain, spinal cord and peripheral nerves

• Nervous tissue is highly specialised between all parts of the body to pass on messages between themselves and other cells in the body

Muscle Tissue

• Contains muscle cells called muscle fibres that are highly specialised for contraction

• Contain the protein actin and myosin, which interact with each other to cause the cells to lengthen or shorten

Plant cells

The organs of the plant can be grouped into 3 systems:

1. Shoot system → part of the plant above ground. it supports the plant, enables the transport of substances around the plant, exchange gases and carries out photosynthesis and reproduction

2. Root system → part of the plant below ground. It’s responsible for absorbing water and nutrients from the soil

3. Vascular system → made up of xylem and phloem vessels

Meristematic Cells

• Found at the tips of roots and shoots

• It’s in these areas the cells divide to produce new growth

• They are cubed shaped and very small

Dermal Tissue

• Protects the plant tissues and and can be found on the outer layer of the stems, roots and leaves

• It protects the plant from damage and controls the interaction s with the plants surroundings

• The epidermal layer is the outermost layer of the dermal tissue

• Most epidermal cells lack chloroplast

Vascular Tissue

• Responsible for the transport of substances around the plant and is found in the roots, stem and leaves

• Xylem tissue transports water and mineral salts from the roots to the leaves

• Phloem tissue transports the products of the photosynthesis around the plant

Ground Tissue

• All of the internal cells of the plant other than the vascular tissue

• This tissue is the bulk of the plant tissue and consists of a variety of different types that are specialised for food storage, support and photosynthesis

Structural Organisation

• A high level of organisation enables the organisms to function efficiently

Hierarchical Structural Organisms

• Organs → different types of tissues that are grouped together to perform a particular function

• Different organs are grouped together to form an organ system that is responsible for a particular bodily function

• Numerous organ systems make up multicellular organisms

Nutrient and Gas Requirements

Autotrophs

• Carry out the process of photosynthesis

• To carry out photosynthesis successfully, most autotrophs require the raw materials carbon dioxide and water

• They also require oxygen to carry out cellular respiration, which provides energy required for all life processes

• Autotrophs also have the ability to convert some of the glucose they produce into other organic compounds such as lipids, proteins and carbohydrates

Heterotrophs

• DO NOT require carbon dioxide because they don’t carry out the process of photosynthesis

• They need to ingest glucose and all other organic compounds because they are not able to manufacture them

• The require the intake of oxygen to carry out cellular respiration to reproduce the energy required by the cells

Similarities

• Both → require inorganic and organic substances, water and oxygen gas

• Autotrophs → require carbon dioxide, produce their own organic nutrients using the energy from the sun and need to obtain inorganic substances such as water, mineral ions and carbon dioxide and oxygen from the external environment

• Heterotrophs → Need to take in all of these nutrients

Autotrophs

• Can produce their own inorganic nutrients and need to obtain water, mineral ions and the gases carbon dioxide and oxygen from external sources

• The majority of autotrophic organisms are plants

• Vascular plants possess a transport system to move substances from one part of the plant to the other

• Non-vascular plants DO NOT possess this transport system e.g. mosses

• All nutrients are absorbed and wastes removed by diffusion and osmosis through the surfaces of the plant

Root System

Main functions:

• Anchoring the plant

• Absorbing water and inorganic nutrients from the soil

The roots have a very large surface area (SA) that allows fro efficient absorption. AN increased SA in roots is achieved by:

• Extensive branching of root system

• The root hair zone (increases SA up to 12x)

• Water enters through the epidermal cells across the entire surface of the root system. The flattened nature of these cells increases their exposed surface

Movement of Substances

• Water moves into the roots by the process of osmosis while mineral ions use diffusion

• Cells of the root can’t photosynthesise as they don’t contain chloroplasts or are exposed to sunlight

• Cellular respiration doesn’t occur, oxygen diffuses into the cells from the air pockets in the soil and the carbon dioxide diffuses out

Shoot System

The 2 main structures that comprise the shoot system are:

• Stems → providing both structural support and a transport pathway between the roots and leaves

• Leaves → absorbing sunlight and carbon dioxide and producing the organic compound glucose in the process of photosynthesis. They are also the site of transpiration, where water evaporates from the leaves

Absorbing Sunlight

• The thin, flat structure of most leaves is suited to this function. A large SA allows maximum absorption of light energy of the chlorophyll inside the chloroplasts of the cell.

• Palisade cells are elongated cells that are dense with chloroplast and are the main photosynthetic cells in leaves.

• Spongy mesophyll cells are situated between the palisade cells and the lower epidermis. They have fewer chloroplast and are irregular in their shape and distribution.

Gaseous Exchange

• Epidermis → a protective layer of cells, the surface of leaves

• Within the epidermis, there are specialised cells called guard cells that control both the exchange of gases and the loss of water through leaves

• Guard cells → occur in pairs and surround a pore known as a stomata

Transport

• Vascular tissue → centre of the root, is continuous, passing through the stem and into the leaves and serves as the main transport tissue in a plant

• Midrib → main vein in the leaf (has many smaller veins branch out from it)

• The veins contain xylem and phloem tissue

Cellular Respiration

• The oxygen required for cellular respiration comes from the oxygen produced as a by-product of photosynthesis

• The carbon dioxide released as a result of cellular respiration is used as a reactant in photosynthesis

• When the rate of photosynthesis is high, the carbon dioxide supply is insufficient, so plants absorb more carbon dioxide from the air

Gas Exchange

Gas Exchange Structures

• All living cells require oxygen and the removal of carbon dioxide

• Surface that gases cross → respiratory surface → movement of these gases is by diffusion

Gas Exchange in Plants

• Structure of leaves → contain open air spaces formed by the irregular shape and arrangement of the spongy mesophyll tissue → increases SA allowing the gases to move freely through the leaf without having to pass through cells

• Most gaseous exchange in plants occurs through the stomata and lenticels

• Larger SA that has been enhanced by folding, branching or flattening allows a faster rate of diffusion

• Moist, thin surface to ensure that the oxygen and carbon dioxide dissolve for easier diffusion. Thinness decreases the distances the gases travel

• Close proximity to an efficient transport system that will transport the gases to and from all cells in the body

• Greater concentration of required gas on 1 side of the membrane than the other, so that a concentration gradient is maintained

Stomata

• Waxy cuticle of leaves in non-porous to both water and gas

• Leaves have pores (stomata) is the epidermis which oxygen and carbon dioxide pass through

• Guard cells contain chloroplasts

• When stomata’s are open → gases can diffuse through them

• When stomata’s are closed → no gases are transported and no water is lost

• The opening and closing of the stomata depend on the environment

Lenticels

• Pores through which gaseous exchange occurs in the woody parts of plants

• Diffusion of carbon dioxide, oxygen and water vapour is relatively slow

Gas Exchange in Animals

• Involves the movement of gases between the external and internal environments by diffusion across the cell membrane

• Gases required by the organism to carry out normal cell functioning move into the cells

• Waste gases produced as a result of these reactions diffuse out

• Respiratory system enables the exchange of gases between an organisms and its environment

Gaseous Exchange in Mammals

• Respiratory systems of terrestrial animals are internal to reduce the loss of water from the respiratory surface

• Occurs in the lungs → alveoli

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

Alveoli

• Increased SA is achieved by approx. 300 million microscopic alveoli that are supplied by 230 million capillaries

• Each alveolus has a thin lining made of flattened cells that are in a single layer, for efficient diffusion of gases across a very small distance

• Surface is moist. The air inside the alveoli is saturated with water vapour and the mucus-lined epithelium reduces the evaporation of this water. This enhances efficient diffusion

• The numerous blood capillaries that closely surround the outside of each alveolus ensure that all alveoli are in close contact with the blood

Gas Exchange in Fish

Gills have characteristics that can extract the maximum amount of oxygen from water

• As water flows over the gills, gaseous exchange takes place

Gaseous Exchange in Insects

• Take in and expel air through structures called spiracles (breathing pores)

• Spiracles have valves to regulate opening and closing

• Achieve gas exchange by tracheal tubes, which carry air directly to the cells of the body

Transport Systems in Plants

Involves vascular tissues arranged in vascular bundles made up of phloem and xylem tissue

Xylem Tissue

• Specialised tissue for the transport of water and dissolved mineral ions from the roots to the leaves. This movement occurs in 1 direction (roots to leaves)

Xylem tissue contains:

• Xylem tracheids → long structures with end walls that tape to a point, where they come into each other and overlap. Water passes from 1 tracheid to another to the other through pits (small holes)

• Xylem vessels

Xylem

• Vessels form continuous tubes for the transport of water

• Cells → specialised xylem vessels = walls break down

• Walls of tracheids and vessels are reinforced with lignin thickening laid down in rings or spirals → help with easy movement of water and dissolved substances and prevent vessels from collapsing

Transpiration-Cohesion-Tension Theory

• The evaporation of water from the leaves creating a pull of water up the stem from roots

• Cohesion → water molecules are attracted to each other and ‘stick’ together

• Adhesion → force between the water molecules and the walls of the xylem vessel cause the water to rise up the sides

Phloem

• Specialised tissue that transports sugars and other products of photosynthesis from the leaves, where they are produced to the rest of the plants where they are used or stored

2 types of phloem cells:

• Sieve tubes → long, thin phloem cells that have large pores through the cell walls (sieve plates) at either end. They are arranged at end to end

• Companion cells → found alongside the sieve tubes and assist the effectiveness of the sieve tube by assisting the movement of sugars

Source-Sink Theory

• Translocation → after glucose is produced in the leaves by photosynthesis, it’s distributed to all parts of the plant

• Source → high pressure region where the sucrose is required

• Sink → low pressure region where the sucrose is required

• Energy pumps sugars at the source of the phloem tissue → draws in water by osmosis which creates a high pressure region at the source

• Difference in pressure drives the movement of substances in the phloem

Imaging Technologies

The development of technologies has led to a greater depth of understanding of not only plant structure but plant functioning

Magnetic Resonance Imaging (MRI)

• Uses radio waves and a magnetic field to take a series of images of the plant structures that are used to produce a 3D image

X-Ray Computer Microtomography (Micro-CT)

• Non-destructive process

• Sample positioned in an x-ray beam is rotated and hundreds of images from different angles are recorded. These are then analysed and reconstructed into a 3D image

Tracing Products of Photosynthesis

• Isotopes → different forms of the same element

• Radioisotopes → isotopes that emit radiation

• Radioisotopes are used as tracers → determine whether the oxygen released during photosynthesis originated from the oxygen atom in water or that in carbon dioxide

Digestive System

Digestion

The breaking down of large and complex food particles into much smaller and simpler particles

• Mechanical digestion → physical breakdown of food.

• Chemical Digestion → digestive enzymes chemically breakdown the large, complex molecules in food that has been ingested into their smaller, simpler forms

Mouth

• Teeth breakdown the food into smaller pieces with greater SA for more efficient action of enzymes

• Salivary amylase is released into the mouth, mixed with the food by chewing.

• The enzyme begins the chemical breakdown of the complex carbohydrate starch into the simpler sugar maltose

Oesophagus

• Food travels along the soft walled, muscle-ringed tube, to the stomach

• As it passes the entrance to the trachea, a flap of skin (epiglottis), closes over the entrance to prevent the entry of food into the respiratory system.

• Peristalsis → muscular contractions move the food

Stomach

• Relaxation and contraction of the stomach walls continue mechanical digestion

• Food combines with gastric juices (chyme)

• Enzyme - pepsinogen is converted into an active form called pepsin to chemically breakdown proteins and nucleic acids

Small Intestine

• Approx. 7m long in an adult

• Contains 3 regions → duodenum, jejunum, ileum

• Chyme enters duodenum → stimulates the release of pancreatic juices into the area

• From the duodenum → food enters jejunum where most of the absorption of digestive products occurs

Absorption in the Digestive Tract

• Amino acids, fatty acids, glucose and glycerol are moved by diffusion or active transport through villi, which line the intestinal wall

• Villi → rich blood supply in the tiny capillaries that are wrapped around a lacteal → glucose and fatty acids are absorbed into the capillaries, while fatty acids and glycerol move into the lacteal

Liver

• When lipids are present in the chyme → bile (produced by the liver and stored in the gall bladder)is released into the duodenum

• Bile breaks down the fats into smaller pieces

• Digested food, once absorbed into the bloodstream, travels to the liver

• Plays an important role in keeping sugars, glycogen and protein levels in balance

Large Intestine

• Undigested material moves her after all required digestive products are absorbed into the small intestine

• In colon → water and some salts are absorbed back into the bloodstream, with undigested material compacting into a more solid substance

• Remaining waste product is moved to the rectum by peristalsis and then eliminated

Circulatory System

Arteries

• Thick muscular walls

• Carry high pressure blood away from the heart

Veins

• Valves

• Carry low pressure blood back to heart.

• Contains valves to control direction of blood flow

Capillaries

• One cell thick

• Diffuse blood directly to and from tissue or organs

How Blood Changes as it Passes

• Lungs → blood becomes oxygenated

• Tissue → decrease in sugars and oxygen, increase in carbon dioxide and wastes

• Kidneys → decrease in wastes

• Intestines → increase in sugars

Transport System in Animals

Circulatory System

• Cells of multicellular organisms require a constant supply of nutrients and oxygen and the continual removal of waste products'

Open Circulatory System

• Made up of one or more hearts and open-ended blood vessels

• Not as efficient as the closed system → fluid pressure is lower, causing the transport fluid to circulate slowly

• Haemolymph → the transport fluid in an open circulatory system → a mixture of blood and tissue

• Exchange of the nutrients and wastes occurs by direct diffusion between the haemolymph and the cells

• E.g. spiders, insects, crabs, snails

Closed Circulatory System

• Found in all vertebrae animals

• Made up of blood vessels and a heart

• Transport fluid → blood → contained in vessels and is pumped around the body by the heart

• Heart pumps blood under high pressure, ensuring efficient transport

3 types of blood vessels:

• Veins → blood carried from organs to the heart

• Arteries → blood carried away from the heart to the organs

• Capillaries → link between arteries and veins

Lymphatic System

• Plays an important role in the defence of the body

• Fluid that surrounds cells diffuse out of capillaries as they pass tissues

• Prevent interstitial fluid (known as lymph) build up → lymph vessels absorb it

• Lymph → flows in lymph vessels from the tissues to the heart → movement is assisted by the contraction of muscles in close proximity of the vessels

• Valves → present in lymph vessels → prevent back flow

Blood

• Fluid transport medium → flows through the heart and blood vessels of the cardiovascular system in vertebraes

• Distributes → heat, nutrients, gases required by the body and the wastes excreted

• Carries → hormones, antibodies and clotting factors

Red Blood Cells (Erythrocytes)

• Function → transport oxygen

• Form in bone marrow

• Oxygen binds to haemoglobin

White Blood Cells (Leucocytes)

• Produced in bone marrow

• Function as part of the immune system

• Several types of WBC each with a specific function in defending the body

• Larger than RBC and not as abundant

Platelets (Thrombocytes)

• Fragments of special cell

• Produced in bone marrow

• Crescent shaped and half the size of RBC

• Function → clotting blood

Plasma

• 90% water and 10% proteins

• Carries → blood cells, plasma proteins, nutrients, gases, excretory gases products, ions, hormones, vitamins

Blood Vessel

• Arteries → blood under high pressure → thick walls to squeeze blood forward

• Veins → blood under low pressure → thin walls, muscles to propel , valves

• Capillaries → extremely tiny, thin vessels → diffusion - slow and passive process

Heart

• Mammals → 4 chambered heart, which pumps blood around the body

• Each side has to chambers → top: atrium, bottom: ventricle

• Composed of cardiac muscle tissue → produces the heart beat when it contracts

• Systemic circulation → pumping of oxygenated blood to all parts of the body and the return of deoxygenated blood to the heart

• Pulmonary circulation → pathway of blood from the heart to the lungs and back to the heart

Composition of Transport Medium

• Function in animals → deliver nutrients and gases to cells and to collect/remove wastes

Changing Composition

• Blood passes through all organs and tissues → concentration of oxygen decreases, concentration of carbon dioxide increases

• Blood moves through lungs → gains oxygen by diffusion from alveoli and removes carbon dioxide

• Blood moves through all of the organs and tissues → nutrients (glucose) move out of the blood and into the cells and the wastes move in the opposite direction

• Increase in glucose and amino acids is seen as blood that has passed through an organ involved in absorbing digested food

Metabolism in the Liver

• Decrease in glucose, fatty acids and amino acids once the blood has passed through the liver

• Glucose may be added or removed

• Urea is added to the blood when proteins are broken down and nitrogen removed

• Toxins and substances such as alcohol are removed from the blood

• Some vitamins and iron are removed