Unit 1 Biology AOS 2 - Functioning systems

What are the methods by which plants regulate and maintain water balance? Why do they need to do this?

• Plants regulate water loss via transpiration and water uptake at the roots

• The xylem losewater if transpiration outweighs water uptake

• Water is essential to plants survival for metabolic reactions including photosynthesis and cellular respiration

What are the methods by which plants lose and gain water and how are they regulated?

Water loss: Transpiration

Regulated by guard cells that surround the stomata, opening the stoma when turgid and closing it when flaccid

Water gain: Water uptake at the roots

Regulated by the amount of active transport of solute at root hair cells that forms the concentration gradient for water

Where is the waxy cuticle located? How does it prevent water loss?

Waxy cuticle: A protective, hydrophobic layer located on the epidermis (the outer cell layer of leaves)

• The waxy cuticle is located on the epidermis and prevents water loss as it is almost completely waterproof and airproof

What enables in water loss (transpiration) regulation of plants? Why must it be regulated?

• Stomata regulate transpiration (water loss)

• They’re generally found on the underside of leaves where there is less sunlight exposure to reduce transpiration

• Stomata need to be open to enable gas exchange for photosynthesis however water is loss in the process

• Hence balancing the rate of photosynthesis and transpiration is a compromise for plants to stay alive

What are the consequences for plants if they don’t balance photosynthesis and transpiration?

Reduced photosynthesis + transpiration:

Insufficient glucose production and reduced therefore cellular respiration which can lead to death

Increased photosynthesis + transpiration:

Viable when water availability is sufficient to replace water lost via transpiration, can lead to death if not

What causes stomata to be open or closed?

Open stomata:

• Guard cells are turgid causing them to pull away and open the stomal pore

• Vacuole absorbs water, increasing in size when guard cells are turgid

Closed stomata:

• Guard cells are flaccid having lost turgid pressure

• They collapse and move towards each other, closing the stoma

Stoma:  The pore of the stomata regulated by the guard cells

What are the factors that affect plants’ rate of water loss? How can they be categorised?

Environmental factors: Temperature, humidity and wind speed
Structural factors: Number of stomata, location of stomata, surface area of leaf

What are the factors that affect plants’ rate of water loss and how do they affect transpiration rate?

Factor	Incorporates	Affect on transpiration when increased
Number of stomata	Changing number to regulate water loss	Increased
Location of stomata	Adaptations to minimise water loss	Location dependent
SA of leaf	Large, curvy + flat leaves with greater SA	Increased
Humidity	Water particles in the air	Decreased
Temperature	Speed and energy of water particles	Increased
Wind speed	Movement of water particles away	Increased

How is water loss regulated by osmosis at the roots?

• Regulate water absorption via the root system

• Driven by the solute concentration gradient that determines the rate of osmosis

• Active transport of mineral ions (solute) into the root hair cells causes water to follow

How do certain plant factors affect the rate of water absorption (osmosis at the roots)?

Factor	Incorporates	Effect on water absorption when increased
Water availability	Amount of water in soil available for uptake	Increased absorption due to greater volume
Mineral ion concentration	Concentration of ions in soil that form the gradient for osmosis	Increased absorption due to stronger gradient
Energy availability in root hair cells	Number of mitochondria that produce ATP needed for active transport of solutes	Increased absorption due to stronger gradient from increased transport

What are the factors that affect the rate of water absorption (osmosis at the roots)?

Includes: Water availability in soil, mineral ion concentration in soil, energy available in root hair cells

• Root hair cells energy is dependent on the number of mitochondria

• More mitochondria increase the rate of cellular respiration and therefore ATP production needed for active transport

What are vascular plants?

• Tracheophytes

• A large group of plants that have vascular tissue (xylem and phloem)

• Vascular tissue conducts water and minerals throughout the plant's roots, stems and leaves

Includes: Flowering plants, ferns and conifers

What are the characterists of seeded vascular plants?

• Includes conifers and flowering plants

• Make up majority of plants on Earth due to easy distribution via seed distribution and flower pollination

What are the characterists of non-seeded vascular plants?

• Ferns

• Make up a small portion of plants as they can't survive in dry environments

• Lack seeds, flowers and fruits and require moisture for reproduction

What are non-vascular plants?

• Bryophytes

• Lack vascular tissue system

• Cycle between sexual and asexual reproduction

• Get water directly from the environment via osmosis

Includes: Mosses, liverworts, hornworts

What are the functions of the shoot system?

1. Provide structural support: Hold leaves, flowers and buds

2. Connect roots to leaves: Transport water + minerals from the roots to the rest of the plant via xylem and sugars from the leaves (sinks) to sources

What are the functions of the root system?

• Can be modified to absorb moisture and exchange gases

• Majority are underground to maximise water absorption

1. Anchoring plant to the soil

2. Absorbing water and minerals:  And transporting them upwards

3. Storing the products of photosynthesis: Made in the leaves, stored as tubers or bulb

What are the plant organs?

• Flower

• Leaf

• Fruit

• Stem

• Root

What are the types of plant tissue?

Dermal (epidermal), ground and vascular

Why do plants need dermal tissue?

• Outer protective layer of the plant

• Protects from injury, pathogens and water loss

• Consists of a single layer of epidermal cells that produce the waxy cuticle

Cells: Epidermal cells, stomata, trichomes

Why do plants need vascular tissue?

• Consists of xylem and phloem

• Control nutrient and water movement

• Cells: Tracheids and vessel elements, sieve tubes and companion cells

Why do plants need ground tissue?

• Forms the bulk of the plant

• Located between dermal and vascular tissue

Function: Photosynthesis, structural support and sugar and water storages

Cells: Parenchyma, collenchyma, sclerenchyma

Why is the xylem made of non-living cells?

• Xylem vessels are long continuous tube consisting of cells arranged end to end

• Made up of tracheids and vessel elements that allow unidirectional flow of water

• Tracheids and vessel elements are dead to be hollow

• Xylem walls contain lignin that provide structural support

• Walls are pitted to allow water exchange with neighbouring cells

What is the function of root hair cells?

• Specialised epidermal cells with long, hair-like extensions that increase SA:V for water absorption

• The site of mineral ion and water absorption via osmosis and active transport

Why do root hair cells have specialised structural features?

• Thin semipermeable cell walls to allow efficient rate of diffusion

• Large vacuole with high solute concentration to encourage water movement via osmosis

• Abundant mitochondria for active transport of solutes

What are the 3 functions of the xylem?

• Water uptake from the roots

• Water movement through the stem

• Loss of water at the leaves via transpiration

How are the xylem vessels part of water uptake?

• Root hair cells actively transport mineral ions into the cells to create a high concentration gradient

• Water follows the gradient into the cells, through the root cortex and into the xylem vessels

How do the xylem vessels transport water?

• The xylem transports water and mineral ions unidirectionally from the roots to the leaves

• This occurs through the cohesion and adhesion of water molecules driven by the transpiration pull

Why is the transpiration stream important?

The continuous, upwards flow of water upwards from the roots, through the xylem vessels to the leaves for transpiration

• Essential for providing ions and nutrients to the leaves, water for photosynthesis, and cooling the plant

• It is a passive process caused by the transpiration pull

How do water molecules cohede?

• Water molecules form hydrogen bonds with each other causing them to stick together

• Form a continuous unbroken chain of water that is draw up via the transpiration pull

How do water molecules adhede?

• Water molecules form bonds with the hydrophilic (water fearing) cellulose walls of the vessels

• Prevents the water column from slipping down and pulls it up the stem

How does water loss (transpiration) occur through the xylem?

Transpiration creates a negative pressure (tension) that pulls water up from the roots through the xylem vessels

What is transpiration?

The loss of water via evaporation at the leaves through stomata

• Assists with the creation of the transpiration pull

What is the transpiration pull?

The negative pressure created by transpiration that continuously draws the water column up into the leaves

• This creates the transpiration stream which is how water moves upwards

What is the function of stomata?

• Allow gas exchange and the facilitation of photosynthesis (C02 in and O2 out)

• Allow water loss to cool the plant

• Assist with the transpiration pull, drawing water and minerals up into the leaves for metabolic processes

What is the structure of stomata?

• Microscopic pores on the epidermis of leaves

• Surrounded by guard cells that regulate their opening and closing

• Contain epidermal cells that surround guard cells

What are guard cells?

Speciliased cells that surround the stomal pore and regulate it's opening and closing

When are the stomata open?

• Occurs during the day when chloroplasts produce glucose via photosynthesis

• This increases the solute concentration in guard cells (hypotonic)

• Water osmoses into the guard cells, they become turgid and bend outwards to open the pore

When are the stomata closed?

• Occurs at night when glucose is used for energy

• Solute concentration in guard cells decrease (hypertonic), water osmoses out

• Guard cells become flaccid and close the pore, remaining parallel and preventing water loss

What processes are involved in the transpiration stream?

1. Water enters xylem vessels through root hairs specialised to maximise water and mineral absorption

2. Water molecules undergo cohesion and adhesion

   • Adhesion: the unlike properties of xylem + water form an attraction

   • Cohesion: Water molecules attract to one another due to same properties of hydrogen

The water molecules rise due to this force

3. Water evaporates from the leaf surface through transpiration

Why is the phloem composed of living cells?

• Composed of sieve element cells (living tissue) which connect to form a tube

• Sieve cells share a sieve plate that allows sugars to pass through bidirectionally

• Companion cells surround the sieve elements to provide structural support

• Made of living cells to allow active transport of sugars

What is the function of phloem?

• Phloem actively transports photosynthesis products bidirectionally from sources to sinks via translocation

• Photosynthesis occurs at the leaves (sources) producing sugars glucose and sucrose

• Translocation of sugars (sap) occurs from the leaves to the other parts of the plants (sinks) 

What is the order of organisation of specialisation?

Specialised cells: Cells with a specific structure for it's particular function

Tissues: A group of specialised cells functioning together for a specific purpose

Organs: A group of 2 or more tissues that work together for a specific purpose

Systems: A group of organs that work together for a specific purpose

What are the 4 types of animal tissue?

4 types of animal tissue: Epithelial, Muscular, Connective and Nervous

What is epithelial tissue?

Tissue made of tightly packed cells that line surfaces

What are the 5 types of epithelial tissue?

1. Squamous (flattened): Alveoli and blood vessel linings

2. Cuboidal (cubical): Kidney and salivary gland linings

3. Columnar (pillar like): Small intestine, uterus, fallopian tubes

4. Ciliated (covered in tiny hairs to move mucous): Trachea - maybe good to remember for exam

5. Glandular (secretory): Endocrine glands

What is muscular tissue and what are the 3 types?

Tissue that makes up muscles and allows movement

Skeletal muscle (voluntary), smooth muscle and cardiac muscle (involuntary)

Why is skeletal muscle important?

• Voluntary

• Allows movement

• Maintains posture

• Stabilises joints

• Maintains body temperature by producing heat via muscle contractions (shivering)

Why do we need smooth muscle?

• Involuntary

• Controls movement of substances through organs (peristalsis)

• Produces the contractions during childbirth from the uterus

• Regulates blood vessel diameter (vasodilation and constriction)

• Regulates airway diameter

Why do we need cardiac muscle?

• Involuntary

• Pumps blood continuously through the heart

• Produces rhythmic, coordinated contractions

What is connective tissue?

Tissue that binds and support other tissues and organs

Remember these types: Blood, bone and adipose

What are the roles of the 5 types of connective tissue?

1. Aerolar/loose: Found under the skin and surrounding vessels and organs, holding them in place EG Subcutaneous layer

2. Adipose: Fat tissue that stores energy

3. Fluid: Transports fluid, nutrients, wastes and hormones EG RBC, WBC, Platelets, plasma (blood) and lymph

4. Supporting: Provide structure and strength to body + soft tissues EG Tendon and ligaments

5. Skeletal: Provides structural support EG Cartilage and bone

What are the 5 types of connective tissue?

1. Aerolar/loose

2. Adipose

3. Fluid

4. Supporting

5. Skeletal

What is nervous tissue?

Tissue of the nervous system that transmits signals

Contains neurons and glial cells

What is the function of neurons and glial cells?

Neurons: Responsible for communication through electrical signals

Glial cells: Supporting cells that maintain the environment around the neurons

How do the effects of hypo and hyperglycaemia differ?

Hyperglycaemia: Damaged blood vessels which can lead to organ failure from inflammation

Hypoglycaemia: Cell death from insufficient glucose absorption which can cause organ failure

How does the pancreas’ functions differ in the endocrine and digestive system?

Endocrine: Regulates BGC through glucose receptors that monitor glucose in blood passing by

Exocrine: Produces digestive enzymes for the duodenum

What is the endocrine component of the pancreas?

• The islets of langerhans: Small, scattered clusters of cells that contain Alpha and Beta cells

• The cells are constantly monitoring BGC in blood to maintain homeostasis (levels are not static)

How does insulin affect blood glucose levels?

• Glucose receptors detect high BGC

• Beta cells secrete insulin into the bloodstream

• Insulin causes absorption of glucose into muscle cells for immediate use, and excess glucose absorption in the liver for temporary storage as glycogen

What functions is glucose used for in it’s locations upon absorption?

1. Fuel: Brain and muscle cells immediately use it to complete cellular respiration for ATP

2. Temporary storage: Liver and muscle cells convert glucose into glycogen

3. Long term storage: Excess glucose that cannot be absrobed is converted into adipose tissue

When are hormones insulin and glucagon released?

Insulin: During the day after meals where BG rises due to carbohydrate breakdown

Glucagon: During fasting, between meals, exercise and sleeping

How does the hormone insulin affect cells?

• Insulin binds to insulin receptors on cells (liver, muscle, fat)

• This opens the glucose channel (protein carrier), allowing facilitated transport of it into the cell

How does glucagon affect blood glucose levels?

• Glucose receptors detect low BGC

• Alpha cells release glucagon into the bloodstream

• Triggers the conversion of glycogen into glucose from the liver cells for release into the bloodstream to raise levels

Explain the process of a changing blood glucose concentration

1. Stimulus: Increase/decrease in BG concentration

2. Receptor: Glucose receptors detect the change

3. Control centre: Alpha or beta cells of the pancreas secret glucagon or insulin

4. Effector: Either the liver cells convert glycogen into glucose and into bloodstream or liver and muscle cells absorb glucose as glycogen for storage

5. Response: Decrease/increase in BG concentration

Negative feedback removes the stimulus

How do changing temperatures affect humans ?

• Humans are endotherms, can be exposed to extreme temperatures for short amounts of time

• However humans enzymes function optimally around 37 degrees

High temps: Dehydration, heat stroke and death

Low temps: Hypothermia and death

What is thermoregulation?

The maintainance of a stable core body temperature within narrow limits

How does the hypothalamus regulate thermoregulation?

• Through thermoreceptors that constantly monitor the temperature and properties of blood passing by

• When level exceed the tolerance limit, it activiates the stimulus response model to return homeostasis

How does the body increase or decrease heat loss from it’s surface?

1. Trapping more or less warm air

2. Sweating and shivering

3. Controlling blood flow by changing blood vessel diameter

How is trapping warm air for insulation a thermoregulatory mechanism?

• Upright hairs on the skin trap more warm air

• Tiny muscles on the skin contract to pull the hairs upright and relax to lay them flat

Upright hairs: Reduce heat loss by forming a layer of warm air (insulation) around the body

Flat hairs: Increase heat loss by allowing warm air surrounding the body to escape

Why do humans sweat as part of the homeostatic mechanism thermoregulation?

• Involves evaporative cooling via sweat

• When the body is too hot, sweat glands secrete sweat onto the skin surface

• Increase heat loss as sweat evaporates off the skin and cools the skin and blood underneath

• Sweating subsides when the body temp returns to homeostatic levels

What does shivering do to assist in maintaining homeostasis?

• Involves rapid, involuntary muscle contractions and relaxations

• Glucosed is used to produce ATP via cellular respiration to enable rapid contractions

• Heat is released as a byproduct which warms the body

How does vasodilation increase heat loss?

• Involves blood vessels widening to increase blood flow

• Blood vessels supplying blood to the skin vasodilate, increasing blood diameter and therefore blood flow

• Increases rate of heat loss as heat is carried to the skin surface and radiates into the cooler environment

How does vasoconstriction reduce heat loss?

• Involves blood vessels narrowing to reduce blood flow

• Blood vessels contract away from the skin surface, reducing heat loss via radiation

• Keeps important, central organs warm and deprioritises extremeties

How does the body thermoregulate when too cold?

Hair muscles: Contract to pull hairs upright to trap a warm layer of air around the body to reduce heat loss

Shivering: Muscles rapidly contract and relax to produce heat as a byproduct of completing cellular respiration
Vasoconstriction: Blood vessels contract away from the skin surface to reduce heat loss via radiation

What are the thermoregulatory responses when the body is too hot?

Hair muscles: Relax to lay hairs flat and increase heat loss via radiation into the environment

Sweat glands: Secrete sweat onto the skin to cool the body as it evaporates

Vasodilation: Blood vessels widen at the skin surface to increase heat loss rate via radiation

Use a stimulus response model to describe the process of thermoregulation

1. Stimulus: Increase/decrease in body temperature

2. Receptor: Thermoreceptors in skin/hypothalamus detect the change in blood

3. Control centre: Hypothalamus determines appropriate response

4. Effector: Blood vessels, muscles and/or sweat glands initiate a response

5. Response: Decrease/increase in body temperature

Negative feedback removes the stimulus

How is sweating a limited thermoregulatory mechanism?

• It relies on the environment being cooler than the body and low in humidity

• High humidity reduces the effectiveness of sweating as there are already water particles in the air

• Sweat remains as liquid on the skin, reducing cooling as evaporation is reduced

What are malfunctions in homeostatic mechanisms?

Diseases caused by the body’s failure to maintain homeostasis

What is Type I Diabetes characterised by?

A disease caused by the body’s inability to regulate blood glucose concentration

How does pancreas function differ in a Type I Diabetic?

• The pancreas produces little to no insulin as the beta cells have been destroyed

• Results in increased blood glucose concentration

• No insulin to bind to the insulin receptors of liver and skeletal muscle cells to absorb glucose

How are Type I and II Diabetes different?

• Type I is generally unpreventable, developed at a young age and genetic

• Type II is developed over time with a poor lifestyle being a large contributing factor to it’s development

Where do the homeostatic malfunctions occur in Type I and Type II diabetes?

• Type I: The pancreas produces little to no insulin due to the destruction of beta cells

• Type II: The liver and skeletal muscle cells are become resistant to insulin, and the pancreas produces insufficient amounts to overcome it

Why is increased thirst a syptom of Type I diabetes?

Increased thirst: From increased urination to excrete glucose in attempt to lower levels

Blurry vision: Eye lens swells due to high levels

Extreme hunger: From inefficient glucose absorption

How does Type I diabetes affect cells?

• Low insulin levels result in skeletal cells particularly to be unable to absorb glucose (no cellular respiration)

• If untreated, can lead to organ failure and death as the cells become starved of energy

How is Type I diabetes treated?

• Patients use prick tests to identify BG concentration

• When high, insulin injections are used to lower BG concentration

• Often injected when eating high sugar meals to correct the increase

What is the condition of Type II diabetes?

A chronic condition where the body is insulin resistant and fails to produce enough of it, resulting in high blood glucose levels (hyperglycaemia)

How does Type II Diabetes develop?

• Lifestyle factors: Obesity, lack of phsyical exercise and poor diet heavily contribute

• Results in insulin resistant body cells (fat,liver,muscle)

• The pancreas cannot produce sufficent insulin to compensate which results in high BG

How are the symptoms of Type II diabetes treated?

Symptoms: Excessive hunger, thirst, tiredness and urination

Treatment: A combination of lifestyle changes to reduce BG levels and medication to improve cells’ insulin sensitivity

What is the condition of hypoglycaemia?

A condition where blood glucose levels drop below the tolerance range

What is the most common cause for hypoglycaemia?

• Diabetes patients taking too much insulin or diabetes medication

Other causes:

• Skipping meals/fasting

• Intense, prolonged exercise

How are the symptoms of hypoglycaemia treated?

Symptoms: Fatigue, sweating, hunger, dizziness

Untreated symptoms: Fainting and seizures

Treatment: Glucagon injections and eating 15g of fast-acting carbohydrates to raise BG

What is hyperthyroidism?

A condition where the thyroid is overactive and produces excessive amounts of the thyroid hormone which accelerates the body’s metabolic rate

How does hyperthyroidism affect the body?

• Bulging eyes and swollen thyroid (goiter)

• Extreme hunger, weight loss

• Elevated heart rate, BP and body temperature

• Muscles cramps and weakness

Is hyperthyroidism caused by a variety of health issues?

• Main cause is the autoimmune disease Grave’s

• More common in men than women (especially 40+)

• The body produces antibodies for the thyroid gland’s receptors

• The antibodies mistakenly stimulate the thyroid gland, resulting in it’s overactivity

How is hyperthyroidism treated?

Medication is taken to inhibit the production of thyroid hormones to reduce metabolic rate

What is the structure and function of the excretory system?

Function: The removal of metabolic wastes and excess water from the body to maintain homeostasis

• Wastes are mainly formed during digestion

Structure: Kidneys, renal vein, renal artery, ureter, bladder, sphincter and urethra

What is the function of the kidneys?

The removal of excretory products from the blood plasma in addition to urine production

How do the kidneys interact with the circulatory system?

• They are connected to the circulatory system via the renal arteries and renal veins

• Renal arteries carry unfiltered oxygenated blood to the kidneys

• Renal veins carry deoxygenated blood to the heart

What is the structure of the kidneys and what are the main features?

• Comprised of millions of nephrons (the functional unit of the kidney) that are embedded in loose connective tissue

Renal capsule: The layer of fibrous, connective tissue that encloses the kidneys

Renal cortex: The outer layer located between the medulla and capsule, where filtration begins

Medulla: The region containing 8-18 renal pyramids with renal columns in between

Papilla: The tip of a renal pyramid that connects into a minor calyx

Renal pelvis: Where urine collects from the calyxes

Describe the functional unit of the kidney, what is its functions in the excretory system?

• Tissues embedded in loose connective tissue

• The nephrons constantly interact with the surrounding capillary network, exchanging molecules between

3 main functions:

1. Filtration of blood

2. Reabsorption of required molecules and water

3. Secretion of unwanted waste molecules