Biology - Thermoregulation

Why is thermoregulation important? Thermoregulation is important as it maintains temperature at an optimal range, within tolerance limits, which allows for the most efficient environment for enzyme activity. Without thermoregulation, enzymes may denature or decrease in activity, or energy isn’t sufficient to allow chemical reactions, leading to a decrease in metabolic activity. Life is sustained by continuous chemical reactions, and if the rate at which these reactions occur is too slow, cells may die and life can’t be sustained.

All methods of Heat Transfer

1. Conduction - Transfer of heat energy from hotter object to cooler object through direct contact

2. Convection - Transfers heat when hot fluid rises and is replaced by a cooler fluid. Creates convection currents. Convection currents of air or water remove heat energy from the surface of an organism as they pass over it

3. Radiation - Movement of heat energy as infrared waves without the need for touching particles

4. Evaporation - Occurs when a liquid turns into a vapour. In sweat, heat is transferred from the skin to the liquid causing it to evaporate. As the water vapour moves off the skin and into the surroundings, it takes the transferred heat energy with it

Endotherms

Animals that use metabolic processes to generate their own heat to maintain their internal temeprataure within their tolerance range

Verterbrate classes: Aves and Mammals

NOTE: There are some species of reptile, fish and insects that are also endothermic or ‘functional endotherms’

ENDOTHERM ADVANTAGES

Decreased vulnerability to fluctuations in external temperature, increased tolerance range (thus larger range of environments it can exist in)

Can be optimally active more times of the day than ectothermic organisms

Increased active times reduce chances of predation

Can maintain high metabolic activity for longer periods of time than ectothermic organisms as they maintain optimal temperature for reactions consistently

Higher body temperatures may increase resistance to fungal infections

DISADVANTAGES:

Higher energy demand than ecotherms of similar size thus higher food intake required - more time hunting/grazing - dependant on constant food supply

Ecotherms

Animals whose internal temperature is determined by the external environment

Ectotherms use the external environment to modify their behaviour to control their internal body temperature

Most reptiles, amphibians, and invertebrates (e.g. insects, crustaceans, molluscs, echinoderms,) are ectothermic

ADVANTAGES: Lower energy demand than endotherms of similar size - environment is largely used to control/regulate temperature therefore food requirements are lower. Less time hunting/foraging, less dependent on constant food supply than endotherms

Generally tolerate higher internal fluctuations in temperature than endotherms

DISADVANTAGES:

Body temperature is dependent on the external environment - limits their distribution to areas with less temperature fluctuations to areas with less temperature fluctuation or less extreme temperatures

Less active times (may be restricted to being active only at night in warm areas or only during the day in cold areas)

May be more susceptible to fungal infections and predation

Cannot maintain optimal metabolism for periods as long as endotherms

Learning Objectives

• Outline behavioural, physiological and structural adaptations of ectothermic organisms for heat loss and heat loss and heat gain

Ectotherms

• Animals whose body temperature is determined by the external environment

• Ectotherms largely rely on behavioural and structural adaptations for thermoregulation

Ectotherms - Structural for HOT ENVIRONMENTS

• May have structures with a high surface area and low volume (High SA to volume ratio)

• When allows them to lose heat more easily in cooler areas

• Lighter colouration

Ectotherms - Behavioural for HOT ENVIRONMENT

• Seeking shade and cooler areas

• More active early in the morning or at night - rest during the day

• Moistening body with saliva or water sources

• Decrease physical activity (thus metabolic activity)

• Increasing surface area exposed to cooler air (not sun)

• Increasing evaporation from body parts (e.g. open mouths)

Ectotherms - Structural for COLD ENVIRONMENT

• Blubber and thick hides

• Darker colouration

• May have high area to volume structures (e.g. Flat body parts) for basking - This can be a negative feature, why? Increase surface area to volume ratio can increase the rate of heat loss out of the system, and can cause a negative effect

Ectotherms - Behavioural for COLD ENVIRONMENT

• Less active during colder times and months

• Increase physical activity (and thus metabolic activity)

• Basking, seeking warmer areas

• Decreasing surface area exposed to cooler air (not sun)

Learning Objectives

Outline behavioural, physiological and structural adaptations of ENDOTHERMIC organisms for heat loss and heat loss and heat gain

MENTAL SET

1) Outline a structural and behavioural adaptation of ectotherms for cold environments. Include specifix examples in your answer

Ectotherms are organisms that rely on thermoregulation via the external environment and aren’t able to produce their own heat via metabolic activity

Structural - High surface area to volume ratio on ectotherms will allow greater heat gain during basking or hotter areas

Behavioural - Sun basking - Sitting out on the sun allows the organism to gain heat via radiation, aiding in maintaining a stable internal body temperature by increasing heat gain

2) Outline a structural and behavioural adaptation of ectotherms for hot environment. Include specific examples in your answer

Structural - High surface area to volume ratio: facilitates heat loss by increasing body exposure to the cold external environment, allowing heat loss via convection or radiation

Behavioural - Seeking darker, shady areas away from the sun in order to promote heat loss via convection or radiation (with the air/breeze)

*FOR THESE QUESTIONS, MAKE SURE TO MENTION THE METHOD OF HEAT TRANSFER

Physiological - HOT ENDOTHERMS

Pilorelaxation - Relaxation of muscles attached to hair follicles (hair erector muscles). Causes hairs to flatten (rather than stand straight). Hairs no longer trap layer of air for insulation. More heat is lost/emitted as radiation and convection, lowering internal temperature

Sweating - Sweat is excreted to the surface of the skin. Heat moves from the surface of the skin into the liquid (via conduction). Liquid then evaporates into a vapour, and the molecules take the heat energy with them. Increasing heat loss via evaporation

Decrease metabolic rate - Rate of metabolic reactions decreases. As metabolic reactions produce heat as a byproduct this also reduces heat productions, which assists in lowering internal temperature (Tends to be a long term response - warmer seasons)

Structural ENDOTHERMS - Cold

Fur, hair, or feathers - traps air between hairs for insulation. When air reaches same temperature as skin there is no more net movement of heat between skin and air - reducing heat loss via radiation and convection

Blubber/Fat - Increases Insulation

Counter-current blood flows in extremities - arteries to extremities and veins from ex

Counter directional flow is important to maintain thermal gradient and thus heat transfer

BROWN ADIPOSE TISSUE - LARGE NUMBER OF MITOCHRONDRIA

PRODUCE HEAT RATHER THAN ATP

BEHAVIOURAL ENDOTHERMS - COLD

Heat seating behaviour

Active during warm periods

Burrowing

Increasing physical activity

PHYSIOLOGICAL - COLD

Shivering - Rapid contraction and relaxation of muscle fibres, requires ATP therefore cellular respiration. More heat produced as a byproduct, increasing internal temperature

Vasoconstriction of superficial (peripheral) blood vessels - Contraction of muscles in walls of skin arterioles, causes blood vessels in surface of skin to narrow. Less blood flow to surface of the skin, reducing heat lost/emitted to environment via radiation, preventing reduction of internal temperature

Piloerection - Contraction of muscles attached to hair follicles (hair erector muscles). Causes hair to stand up striahgt, trappin hair between hairs. Air acts as insulating layer - when

Increasing metabolic rate - rate of metabolic reactions increases,

Increase in metabolic rate for heat production also increases food demands. If food is scarce animals may instead enter torpor - a state of decreased metabolic rate and physical activity. Torpor reduces energy and water needs for the organism, but internal temperature can drop significantly

Hibernation is an extended period of torpor where the metabolic rate falls to a level that just sustains lfie - significantly reducing energy demands

Aestivation is another form of long term torpor, typically used in very dry conditions (More for water retention rather than heat)

Kleptothermy - Animals sharing or stealing body heat (Bunching up)

Explain how a greater bilby’s ears could help it to thermoregulate

Thermoregulation is a mechanism that allows the maintenance of an organism’s internal body body temperature at a stable, constant level, within tolerance limits.

Large, flat ears increases surface area to volume ratio. This can facilitates greater heat loss via radiation or convection (with cold air), as more skin is exposed to the environment aiding in thermoregulation when it’s hot.

Large ears provide greater vascularity. Increased vascularity to the ears allows greater blood flow, bringing heat from the core (via the blood), allowing greater heat loss through the ears.

Increase blood supply to increase heat loss or decrease blood supply to reduce heat loss

Hairless ears make heat loss more efficient or there is no insulation (to trap air close to the body) or the surface of the ears is in direct contact with the air

INVESTIGATION QUESTIONS:

a) Identify the trend shown by the python’s and eagle’s temperature and propose a reason for these trends (4 marks)

The python displays a decrease in average internal temperature as time begins to elapse, in a linear trend with no fluctuations *The python’s temperature remains relatively stable around 22 degrees for 20 minutes. After 20 minutes the pythons temperature decreases over time reaching 14.6 degrees at 60 minutes (1 mark)

An explanation for this trend is that python’s are ectotherms whose internal body temperatures are heavily reliant on the external environment. As the temperature of the enclosure was reduced to 10 degrees celcius, the internal body temperature of the python decreases to follow it, as it does not have any homeostatic mechanisms that allow it to generate heat to increase it’s body temperature.

Ectotherms also have a broader tolerance range compared to endotherms

The Eagle Owl’s temperature remains at a relatively constant average internal temperature at (40 Degrees), with small fluctuations over time

An explanation for this trend is that the Eagle Owl is an endotherm, whose internal body temperature are regulated via thermoregulatory mechanisms. As the temperature of the encloure was reduced to 10 degrees celsius, the Eagle Owl’s thermoregulatory systems acts in order to counteract the change. This leads to it increasing its internal body temperature, creating the fluctuations seen in the graph, however maintains a relatively stable, constant internal body temperature. Endotherms also have a smaller tolerance range compared to endotherms

Predict the temperature of the python at 55 minutes (1 mark) - 15.5 degrees celsius.

1) Aim: To investigate the average internal temperature of Stimson python and Eurasian Eagle Owl over 60 minutes (when temperature is reduced at 20 minutes) *CORRECT

2) IDV: Type of animal/organism experimented on - Eurasian eagle owl and Stimson Python *Correct

3) DV: Average Internal temperature of organism (over time, in degrees celsius) *Correct

4) Controlled Variable
Environmental factor e.g. (humidity of enclosure, size of enclosure, ambient sunlight, rate of cooling (or something like that))

Activity level of organisms

Relative size/mass of organisms used

Method of recording internal temperature (cloacal thermometer)

Health status of the experimentees (diseases, etc)

Ages/Developmental stage of the animals (e.g. Young adults relative to their age)

Room temperature is maintained at a constant 10 degrees celsius.

5) Hypothesis: As time elapses in a room at a temperature of 10 degrees celsius, the Eurasian Eagle Owl’s body temperature will remain relatively constant, while the Python’s body temperature will slowly decrease near 10 degrees celsius. OR the temperature of the owl will remain higher than the temperature of the python over time

Identify an ethical concern this experiment raises and discuss how it could be mitigated (2 marks)
Physical harm/stress towards the organism. A way to mitigate this is to change the temperature that’s being reduced to a higher level, within the animal’s tolerance limits.

1) Describe what is meant by the term animal ethics and state 3 considerations that should be made when undertaking research involving animals (4 marks)

• Animal ethics refers to considerations regarding procedures that may cause physical and psychological harm towards an organism/animal

• Reduction - Refers to a decrease in the quantity of animals experimented on

• Refinement - Improving experimental qualities in order to ensure less animal harm

• Replacement - Researchers must seek alternatives to replace animals with more viable and ethical methods

*CORRECT ANSWER

• Animal ethics involves consideration of respectful, fair and just treatment treatments of animals.

• The use of animals in science involves consideration of

• Replacement - substitution of insentient materials for conscious living animals

• Reduction - using only the minimum number of animals to satisfy research statistical requirements,

• Refinement decrease in the incidence or severity of ‘inhumane’ procedures applied to those animals that still have to be used.

INVESTIGATION TABLE

Temperature of water in test tubes insulated with different materials over 20 minutes

                                                                                TIME (Minutes)

Temperature of water in test tubes

Water’s most significant intermolecular force is hydrogen bonds. In order for a molecule to be soluble in water, the molecule must contain intermolecular forces that areh equal to or are stronger than hydrogen bonds, in order to break the bonds and bind to water and ‘dissolving’

1. Outline the difference between primary data and secondary data (2 marks) Primary data refers to data that has been directly collected by a person to be used by the person, while secondary data refers to data that has been received from a another reliable source/person

2. Accuracy refers to how close an experimental/measured value is to it’s actual value.

   1. Reliability refers to how repeatable an experiment’s results are. The extent an experiment returns consistent results

   2. Validity refers to whether an experiment’s results are representative of what it’s supposed to be testing - Test the hypothesis

3. Measurement error is a form of systematic error where a data value is read incorrectly. It is usually resolved by included absolute value, of +- 1 - Error caused by the difference between the measured value and the actual vallue

ACTUAL ANSWERS:

• Accuracy refers to how close an experimental/measured value is to it’s actual value.

• Reliability: The degree to which an assessment instrument or protocol consistently and repeatedly measures an attribute achieving similar results for the same population

• Validity refers to the extent to which tests measure what was intended; the extent to which data, inferences and actions produced from tests and other processes are accurate.

*Shivering is the rapid contraction and relaxation of muscles, which requires energy (ATP), increasing cellular respiration and producing heat as a byproduct

When the liquid evaporats into vapour, molecules take heat with it to the external environment, therefore causing heat loss from the body.

a) Identify which type of adaptation the outer covering is: Structural adaptation

b) Some lilijani species are born without the protective covering and steal the covering of their siblings. Classify this type of adaptation (1 mark) Behavioural

c) The function of the dense fibrous, protective outer covering on its cranium acts as a thermal insulator, trapping heat and preventing heat loss. Due to its fibrous structure, it can prevent heat transfer from the environment through radiation, which can assist in Lilijani yappinus maintaining heat in cold environments

Torpor and estivation are both states of dramatically reduces physiological activity, metabolic activity, and lowered body temperature. Torpor’s mainly to reduce energy demand, while estivation is mainly to retain water and prevent dehydration

WHAT ARE THE THREE R’S

Reduction - To only use the minimum number of organisms to satisfy research requirements

Refinement - To decrease in the incidence of severity of inhumane procedures procedures applied to organisms being experimented on

Replacement - To switch conscious, living animals with insentient objects

b, c, a, c

What are the advantages and disadvantages of urea/

• Advantages: Can be stored as a concentrated solution

• Has a low toxicity (lower than ammonia and urea)

• Can be used for development of young in eggs (because it has low toxicity)

Disadvantages:

Has a high energy cost to produce because it is more complex than ammonia and urea.

1) Osmoconformers are organisms are isotonic to their environment and solute concentrations in their cells are equivalent to the environment. Osmoregulators are either hypertonic or hypotonic to their environment and use physiological/structural processes that allows the counteraction of osmotic potential of the environment.

FRESHWATER FISH

What are problems affecting freshwater fish:

• Lower salt concentration in surroundings than cells

• Higher water concentration (osmotic pressure) in surroundings than cells

• The surrounding is hypotonic to cells

• Cells are hypertonic to surroundings

• Fish are hypertonic to their surroundings - their blood has a lower water concentration than the surrounding fresh water

• Water molecules diffuse from the fresh water into the blood by osmosis

• Osmosis (passive water movement) into the cells

• As fresh water passes through the mouth and over the gill membranes, water molecules diffuse from the fresh water into the blood by osmosis

• These fish must produce a very large volume of dilute urine to balance this large intake of water

• This large volume of urine carries salt with it, and the salt has to be replaced

Solutions/Adaptations

Must produce a very large volume of dilute urine to balance this large intake of water → high filtration rate in kidneys = large number of glomeruli

**Gills are highly vascularised, has higher SA, and highly permeable

Eac hill consists of fleshlike, threadlike, filaments

Structural Adaptation - Large number of glomeruli

Chloride secretory cells in the gills

Scales/Mucous layer

Physiological Adapation

Actively transport salt

Selective reabsorption of salts/ions in kidneys by active transport

Producing a Large volume of urine

Behavioural Adaptation

Don’t drink water

Freshwater

• Salt concentration is higher/hypertonic in fish compared to freshwater or lower/hypotonic in freshwater compared to fish

• Fish tends to gain water and/or lose salt

• Kidneys produce large volumes of dilute urine

Salt Water Fish

Mental Set

1. Identify the type of nitrogenous waste produced by:

   1. Reptiles - Uric acid

   2. Aves - Uric acid

   3. Freshwater fish - Ammonia

   4. Adult amphibians - Urea

   5. Mammals - Urea

   6. Larvae Amphibians - Ammonia

   7. State an advantage of uric acid production - Low toxicity (for reptiles it allows eggs to develop without getting damaged), Water conservative

   8. State an advantage of ammonia production - Low energy demand

   9. State an advantage of urea production - Median between both. Lower energy cost than uric acid, More water conservative than ammonia.

Bio Test Task 6

c) d) Scientific studies have shown that none of the heterothermic australian species has gone extinct. In contrast many of the similar-sized homeothermic species, such as rodents and bandicoots, have suffered high rates of extinction. Discuss how torpor helps to improve the survival rate of Australian animals

Torpor reduces energy demands (1) this reduces food/water requirements in which is beneficial in areas with low supply of resource (1)

c) Describe the relationship between air temperature and the colour rating of grasshoppers (2 marks)

Trend (1) and data (1)
As air temperature increases colour rating of active grasshoppers decreased (1) As shown where an air temperature of 3 degrees resulted in a colour rating of 3.75 and an air temperature of 12

f) Grasshoppers are ectothermic (1) so cannot move around at night as they are not able to regulate their temperature in the cold environment (!)
Some predators are endothermic (1) so can move around at night as they are able to regulate their temperature in the cold environment (1)

3) Reason 1 and explanation: Predatory/More Active/ Large so would have higher energy demands (1)

In order to be active at more times they would need to regulate their own temeprature OR would require consistently high metabolic rate (which is only provided by endothermy)

Reason 2 and explanation: Low SA to Volume ratio: Therefore requires themoregulation through physiological processes as the environment is not sufficient enough.

d) Explain why the changes in tail temperature decsribed in your answer to c) are of greate benefit to the animal? (2 marks)

Reduced temperature of the tail reduces heat lost to the environment (1) allowing core body temperature to remain stable/retainss heat in core of body (1)

e) What do the graphs tell you about the possibility of the tail playing a part in heat loss as well as in heat conservation? (2 marks)

Tail temperature increased after exercise (1) indicating it is used as a source of heat loss (via radiation)

Mental Set

1. Describe why plants need oxygen - For cellular respiration

2. Describe why plants need carbon dioxide - Photosynthesis to use for energy

3. Describe why plants need water - To allow for cellular function, maintain cellulose and cell walls, use as a medium to transport wastes and nutrients, used for photosynthesis, cells to be turgid rather than plasmolosysed

4. Describe how plants obtain water - Via roots carrying up through the xylum

5. Identify where gas exchange occurs in plants - The leaves - Stomata (underside)

Question Set 11.5

1. State the relationship between the following factors and the transpiration rate:

   1. High light intensity - Increased transpiration rate. Photosynthesis is induced due to abundance of light, causing stomata to open, causing water loss, therefore increased transpiration

   2. Low temperature - Decreased transpiration rate. Low temperature prevents energy required for latent heat of vaporisation, casing less evaporation into water vapour from the stomata

   3. High wind - Increase transpiration rate. High winds induce pressures onto the leaf, replacing the thin layer of saturated air with unsaturated air, maintaining a steeper concentration gradient with allows more water to evaporate and diffuse faster.,

   4. Low humidity - Increases transpiration rate. Low humidity allows water in leaves to evaporate without much difficulty/prevention, as there is an increased concentration gradient between surrounding air and the interior of the leaf

2. Describe the role of the guard cells in regulating water loss in a plant - Guard cells are responsible for the opening/closing of stomata in response to increasing and decreasing water pressures within the guard cells. Swelling of guard cells cause the stomata to open, and shrinking causing it to close. They regulate transpiration, which allows intake of gases to be used for photosynthesis, while shutting to prevent water loss in dry, hot conditions

   1. *The opening and closing of the stomata is controlled by the guard cells. Light stimulates opening of stomata. By the use of active transport, Potassium ions K+ are purposely moved into guard cells. This creates a concentraiton gradient. Guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost, guard cells become flaccid and the inner walls moves together closing the pore, decreasing water loss

1. Differentiate between the terms ‘transpiration’ and ‘transpiration pull’ - Transpiration refers to the loss of water through leaves due to evaporation. Transpiration pull refers to the forces of adhesion and cohesion that aids in creating a continuous water column up from the roots to the stems.

2. Explain why transpiration cannot continue without evaporation.

   1. In order for water to be lost from the leaves, evaporation must occur so water molecules can be carried into the surrounding air via water vapour.

Plants and Water Pt. 1

The Life Cycle of a Plant

Plants begin as seeds or spores

Grow to maturity

Then, sexually reproduce sexually or asexually. (Sexually are flowering plants and asexually is non-flowering plants)

Photosynthesis is performed throughout a plant’s life

Plant Requirements

Water and minerals enter the plant through the roots

Carbon dioxide and light energy enter the plant through the leaves

Byproducts of photosynthesis, water and oxygen, exit the plant through the leaves

Photosynthesis: 6CO2 + 6H2O → C6H12O6 +6O2

Plant Structures

Like most other multicellular orgnisms, plants have specialised system of organs, tissues, and cells

3 Tissue Types in Plants

Dermal: protective outer covering

Vascular: vessels support the plant and transport water and nutrients

Ground: where photosynthesis takes place

Dermal Tissue

Protective outer covering

In non-woody plants, the “skin” of the plant is called the epidermis

May be specialised, e.g. leaf epidermis secretes the waxy cuticle

In older plants, dermal tissue may be very thick and covered in bark

Vascular Tissue

Long, slender vessels, arranged in bundles, that transport water, minerals, and organic molecules between roots and shoot

Contributes to structural support

Two types: Xylem and Phloem

Vascular tissue is located in the center of roots

Leaf veins are bundles of vascular tissue

Xylem & Phloem

In Roots:

Xylem: Moves water and minerals up from roots to the stem

Dead cells that transport water and dissolved minerals upward from roots to shoots

Phloem: Carries sugar from leaves down the stem and into roots (can be either direction)

Living cells that transport nutrients and carbohydrates produced by photosynthesis throughout the plant

Ground Tissue

Fills spaces between dermal (1) and vascular (2) tissues

Functions in photosynthesis, sugar storage, and support

Makes up most of a young, non-woody

Function of Stems

Support leaves and reproductive structures

Contain vascular tissue that transports sugars and water throughout plant

Function of Leaves

Carry out photosynthesis

Capture light

Exchange gases with the atmosphere

Minimise water loss

Leaf Anatomy

Flat for greatest exposure to sunlight

Closely packed cells of palisade mesophyll gather light

Loosely packed cells in spongy mesophyll allow for exchange of gases and water

Air spaces in the spongy mesophyll allow the movement of carbon dioxide, oxygen and water vapour between the palisade layer and leaf openings in the lower epidermis

Cuticle

Waxy coating on leaves and other plant parts that helps retain moisture

Secreted by cells in the epidermis

Stomata

Microscopic pores in the leaf surface, usually on the underside

Allow for the exchange of oxygen and carbon dioxide

Can be closed to prevent water loss

The singular of stomata is stoma

Floating leaves, such as those of lily pads, have stomata in the upper epidermis

Guard Cells

Two Guard Cells surround each stoma and control its opening and closing, therefore regulating the movement of gases such as CO2 and water vapour

Stomata open and close in response to increasing and decreasing water pressure within the guard cells

When plenty of water is available, water pressure in the guard cells increases, the cells swell, and the stoma opens

When water is scarce, water pressure decreases in the guard cells causing them to shrink. This closes the stoma and reduces water loss

Generally, stomata are open during the day for photosynthesis and closed at night to conserve water

PLANTS AND WATER P.T 2

Why is water balance and moderate temperature vital for the functioning of a plant?

Water is essential for:

Maintaining cell turgidity for structure and growth

Transporting nutrients and organic compounds throughout the plant

Serving as a raw material for various chemical processes, including photosynthesis

Temperature enzymes do not function at very low or vey high temperatures

Enzymes will denature at high temperatures and at very low temperatures the substrate-enzyme bonds will not occur frequently.

How it’s done:

1. Osmosis

2. Capillary action - adhesions (adhering to walls of the xylem, in the pits), cohesion

   1. Cohesive forces between the water molecules e.g. holding hands

3. Transpiration

4. Negative/low pressure, causing high pressure - enough to get water up 100m, top of trees! Osmosis can only move water a couple of metres.

Forces in the leaves

Transpiration - Water lost from leaves

Evapo-transpiration - Water lost from leaves as water evaporates

Transpiration stream - Water is pulled up the stem as water is lost from the leaves in transpiration (continuous stream)

Adhesion - Water molecules stick to the sides of the walls in the xylem

Cohesion - Water molecules stick to each other

Capillarity/capillary action - Water is drawn upwards through thin tubes

Movement of Water Up Xylem Vessels

When water enters the roots, hydrogen bonds link each water molecule to the next.

So the molecules of water are pulled up the thin xylem vessels like beads on a string.

The water moves up the plant, enters the leaves, moves into air spaces in the leaf, and then evaporates (transpires) through the stomata (singular, stoma)

Forces in the Roots

Active transport - Salts are actively absorbed, increasing the osmotic pressure within the roots (low to high)

Osmosis - Water is pulled in due to the concentration gradients (water moving from a high concentration of water to a low concentration of water)

Movement of Sugar

Translocation - Movement of sugar - the sugar is actively transported from leaf to phloem (source) and from phloem to roots (sink), thus setting up a concentration gradient from leafs to roots

Diffusion - Sugar will diffuse downwards because of this concentration gradient

Osmosis - Water will be pulled out of the xylem near the leaves, and move downwards, then return to the xylem near the roots, due to the concentration gradient.

Plant Transport Systems

Leaves - Carry out photosynthesis and transpiration

Stomata - Allow water and gases (carbon dioxide, oxygen) to enter and leave the leaf. Opening is controlled by guard cells

Xylem - Transports water and salts upwards

Phloem - Transports sugars, (translocation) mostly downwards

Roots - Draw in water and salts

Root hairs - Increase surface area

Leaves and Stomata

There are hundreds of stomata in the epidermis of a leaf.

Most are located in the lower epidermis

This reduces water loss, because the lower surface receives less solar radiation than the upper surface.

Each stoma allows the carbon dioxide necessary for photosynthesis to enter, while water evaporates through each one in transpiration

Structural Adapations of Leaves and Stomata

Leaves are responsible for photosynthesis and exchange of gases and water

Gases and water enter and leave through the stomata

Epidermis provides protection

Palisade cells carry out photosynthesis

The spongy mesophyll layer allows storage of air and water vapour

Vascular bundles contain xylem and phloem for the transport of water, salts and sugars

Control of stomatal opening

Stomatal opening is controlled by turgor pressure in the guard cells

This is controlled by pumping salts into the cells and glucose increasing with photosynthesis, thus bringing in more water (opening stoma) or pumping salts out of the cells, thus forcing water to leave (closing stoma)

Turgor pressure increases when water availability is high
Turgor pressure decreases when water availability is low

When guard cells are turgid, under pressure from the water they contain, their outer elastic walls bend more than the inner thickened walls, causing the stomatal pore to increase in size and the stomata to open

Guard cells are cells surrounding each stoma. They help to regulate the rate of transpiration by opening and closing the stomata.

Turgidity is caused by the accumulation of K+ ions in the guard cells. As K+ levels increase in the guard cells, the water potential of the guard cells drops, and water enters the guard cells.

Guard cell Function

Stomatal closing

Potassium ions move out of the vacuole and out of the cells

Water moves out of the vacuoles, following potassium ions

The guard cells shrink in size

The stoma closes

Stomatal Opening

Potassium ions move into the vacuoles.

Water moves into the vacuoles, following potassium ions.

The guard cells expand

The stoma opens.

Plants and Water PT 3

Structure in the stem

Root Hairs and Water Transport

Water moves in by osmosis

Osmotic pressure in root hair cell is higher than in soil

This can be maintained by active transport of salts into the root hairs

Root hairs increase the surface area available

Measuring Water Loss

This can be done with a device called a potometer

The rate of transpiration is shown by movement of a bubble of air through the tubing

Key features include - air tight seal between plant and tubing, narrow tubing intact stem (cut under water so it will draw up water), air bubble, scale

Water loss in plants

Factors affecting water loss

Temperature

Humidity

Air movement

Water availability

Light intensity

Decreasing water loss also decreases photosynthesis

Plant adaptations - Arid (HOT AND DRY)

Problems faced

Water availability low

Humidity low

Temperature high

Light high

Air movement high

Solutions include

Increased roots - either deep or wide and shallow

Water storage (roots, leaves or stems) e.g. cacti, boabs

Reduced leaves

Reduced stomata in leaves

Protection for leaves - cuticle, thick epidermis, curling, sunken pits, hairs to guard stomata
Closing stomata in hot conditions

Plant adaptations - Coastal (Hot AND DRY AND SALINE, AND SANDY)
Problems faced
Water availability low

Humidity low

Temperature high

Light high

Air movement - High, lots of sand and salt

Solutions include
Wide shallow root systems

Rapid growth

Can cope with burial

Rolled leaves, sunken stomata, reduced stomata, and/or hairs

Succulent leaves

Salt secretion in leaves

Plant adaptations - Humid (Such as rainforests, low light, high humidity)

Problems faced
Water availability high

Humidity high

Temperature varies - high (tropical) to medium (temperature)
Light can vary - high in the canopy, low at ground level.

Air movement - Usually low

Solutions include

Large leaves to trap light

Deep veins to carry water away from the plant

Usualy many stoma and thin epidermis

Large air spaces within leaves

Plant adaptations - Aquatic Environment (Lots of water, lack of air, high salinity)

Problems faced

Water availability high

Humidity usually high

Temperature varies

Light usually high (may vary if plant deeper under water)

Air low

Solutions include

Stomata on surfaces of leaves (e.g. water lillies)
Large air spaces for buoyancy and gas storage

Aerial roots (e.g. mangroves)
Salt secretion in leaves (mangroves)

Plant adaptations - Cold and Arctic environments (Cold, restricted water availability in winter, reduced light, severe wind)

Problems faced
Water availability seasonal - low at some times, higher at others

Humidity - seasonal. Low at some times, higher at others

Temperature - Seasonal - Low at some times, higher at others

Light - Seasonal. Low at some times, higher at others

Air movement - Seasonal. Low at some times, higher at others

Solutions include
Deep roots systems

Annuals - rapid growth, seeding and then die over winter

Bulbs - Leaves die back during winter

Rolled leaves, reduced leaves (conifers)
Dropped leaves and dormancy (deciduous trees)

Antifreeze sap or resin in conifers - prevent cells bursting when frozen

Hydrophytes - Plants which have adapted and evolved to live in extremely wet conditions. ‘hydro’ = ‘water’ e.g. water lily, duckweed

Halophytes - Plants that grows in waters of high salinity, only ~2% of plant species are halophytes e.g. mangrove trees 5

Reduced number of leaves

Reduced size of leaves

Few stomata

Sunken or protected stomata

Hairs covering leaves

Thick, waxy cuticle

Accumulation of salt in older leaves

Accumulation of salt in salt bladders

Salt glands that secrete salt ACTIVELY

Succulence - Water storage structures in leaves and stems

Root cell filtration

Actively accumulate salt in roots

*Each of these features acts to reduce water lost by transpiration

Xerophytes - Plants adapted to survive under very poor availability of water (e.g. desert, arctic) e.g. cacti, spinifex, marram grass

Reduced leaf surface area exposed to the sun e.g. curly

The leaves of Spinifex roll into a tube during the hottest part of the day

Curling up also traps a layer of moist air, decreases transpiration rate

Hakea have needle-shaped leaves to reduce the SA over which water can be lost

Fewer stomata, which are sunken in grooves in pits

Pit may be surrounded by hair which slows down transpiration

Stomata can close during hottest part of the day

Acacia reduce water loss with hair leaves and stems for insulation, and silver hairs to reflect the heat

Eucalyptus have leaves that hang vertically, reducing SA exposed to sun

Reduced number of leaves

A tap root which can reach deep for soil water and an extensive surface system to absorb water

Sunken stomata - Having the stomata sunken in a little bit creates an area of humidity, reducing water loss via evaporation.

Rolled leaves

Thick, waxy cuticle

Shallow, spreading roots - To reach a larger area to capture precipitation (since sand is very permeable)

Storage of water in succulent tissues

Mesophytes - Plants growing in an environment which is neither dry nor very wet, ‘meso’ = middle e.g. tulips, grasses.

Mental Set

1. Identify the parts of a negative feedback loop - Stimulus, receptor, modulator, effector, response, feedback

2. Xerophytes

3. Deserts, Antartica

4. Halophytes

5. Oceans, salt-water lakes, mud flats, and estoeries

Xerophytes - Plants adapted to survive under very poor availability of water (e.g. desert, arctic) e.g. cacti, spinifex, marram grass

Command: Explain
Concept: High salinity adaptations of plants

Condition: High salinity soil, halophytic plants

Critical - High salinity, harmful, halophytic plants, overcome problems

Context: High salinity in sil is harmful to many plants

Explain why high salinity in the soil is harmful to many plants and how halophytic plants overcome the problems caused by high salinity.

High salt concentrations in the soil causes the plant to lose water from the cells to the soil via osmosis. This is because the plant is hypotonic to the environment, decreasing the water gradient and causing it to diffuse out of the cell. This can induce plasmolysis, where the cell wall breaks down due to lack of water and become flaccid. Halophytic plants are able to overcome this issue due to adaptations such as high rise roots and salt excretory glands. In plants such as mangroves, high rise roots reduce the surface area and exposure to the

Command: Explain

Concept: Thermoregulation
Condition: Open and closing the body feathers, increasing decreasing blood flow, maintain constant body temp

Critical: Opening and closing of feathers (piloerection, pilorelaxation) Decreasing and increasing blood flow (vasodilation & vasoconstriction)

Context: How it can help emus, talk about their environment potentially

Explain how opening or closing the body feathers to airflow and increasing or decreasing blood flow to the leges can help emus to maintain a constant body temperature over a broad range of environmental temperatures

Command: Explain

Concept: Osmoregulation

Condition: Three methods, bony fish, sea water AND in fresh water

Critical: Maintain salt and water balance - Fresh water & salt water scenarios, CHALLENGES they face
Context: Bony fish, maintaining water and salt balance in different environments

Explain the challenges that a bony fish faces in maintaining water and salt balance in fresh water and explain three method that a bony fish uses to maintain water and salt balance in sea water.

A bony fish such as carp experiences challenges regarding solute concentrations of their cells and the external environment. In fresh water, the cells of the bony fish is hypertonic to the environment. This causes water to enter the cell from the environment via osmosis (through the gills). Salt is removed from the cells via diffusion from high to low concentration from the cells to the environment.

In salt water, the cells of the bony fish is hypotonic to the environment. This causes water to leave the cell into the environment via osmosis. Salts in the water diffuse from high to low concentrations into the cells of the fish. In order to counteract this, short/long nephrons, chloride-secretory cells. Scales are impermeable, preventing water from diffusing from the epidermis into the environment

Maintaining water and salt balance in sea water: Drinks seawater to replace lost water

Produces concentrated urine or produces a small volume of urine to remove excess salt or minimise water loss

Expels excess salt via activate transport across the gills

Why do plants need to maintain water and thermal balance

Fish living in salt water and freshwater, provide an example, explain challenges, adapations,

Why can larger animals dive deeper into the ocean

Plant adaptation in an arid environment