Mitosis vs Meiosis

 

Mitosis

• in all body cells EXCEPT SEX CELLS
• for growth…repair…asexual reproduction

Meiosis

• in sex cells
• for sexual reproduction

Increasing Accuracy, Reliability and Precision

Accuracy – How close a measurement is to the TRUE value

to increase accuracy, e.g. RE-ZERO a scale, read from a horizontal distance (avoid PARALLAX, position object at ZERO OF A RULER

Reliability – Repetitions

Precision – Decimal Places

Transpiration, Xylem Vessels and Phloem Tubes

Cambium immature cell (could become either a xylem or phloem cell)

Tissue	Xylem	Phloem
Transport	Water an minerals from roots to shoots and leaves	Sucrose and amino acids produced in leaves during photosynthesis to every part of the plant
Process	Transpiration	Translocation
Structure	Cylindrical cells arranged end to end, in which the cytoplasm dies and the cell walls between adjoining cells breaks down leaving a dead empty tube with strengthened cell walls	Phloem tubes are made up of columns of living cylindrical cells. The cell walls between adjoining cells develop holes like a sieve allowing transport through the tube

XYLEM VESSELS: Why does the water move up? What is the “transpiration stream”?

“Water is lost through the leaf of the plant by evaporation in a process called transpiration. This results in a pull on a column of water molecules which extends right down through the stem to the roots.

Water molecules are held together by hydrogen bonds. As a water molecule evaporates from the leaf, it pulls on the water molecule next to it, which in turn exerts a pull on the water molecule next to it and so on. This transmits a pull all the way down the column of water to the root system. In addition, the water molecules also adhere to the walls of the xylem vessel, preventing gravity from pulling the molecules back down.

So as each water molecule exits the leaf, it pulls the column of water molecules upwards from the root of the plant up the xylem and into the leaf. This upward movement of water resulting from the evaporation of water from the leaf is called the transpiration stream.” (from Pass My Exams)

24/10/13

Translocation

Sucrose is glucose molecules bonded together (in a condensation reaction). Sucrose can get broken down into glucose which is used for

• releasing energy by respiration
• producing proteins, such as enzymes and chlorophyll
• producing cellulose, which strengthens the cell wall

*NOTE: Plants also need nitrates (absorbed from the soil as nitrate ions)

1. Nitrates are used to make amino acids…
2. Amino acids are needed to make proteins…
3. Proteins are used to help plant grow

ALL THE STEPS ABOVE ARE NEEDED FOR MAX. MARKS IN EXAM QS. “NITRATES HELP PLANT GROW” IS REJECTED.

Sucrose is transported to:

• shoot tip
• root tip
• fruits
• flowers (pollen production)
• etc

Transpiration the evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata

• Q: Why does more transpiration happen during the day than at night?
• A: Higher light intensity triggers stomata to open + higher temperature decreases the concentration of water vapor particles outside the leaf because heated particles have more kinetic energy and spread out away from the leaf

• Q: Suggest how plants cope with hot, dry conditions
• A: long and narrow leaf/spines/less stomata/hairs (water vapor particles passing out of the leaf clump together into droplets which attach to the hairs – this balances out the concentration gradient because the hairs are outside the leaf)

Why are there more stomata on the bottom of the leaf?

General idea: MINIMISES WATER LOSS: THE PLANT DOES NOT WANT TO LOSE WATER.

• Gas exchange would occur faster if there were more stomata on top because more sunlight hits the top (light causes stomata to open and the stomata are the site of gas exchange). If there were more stomata on top, a lot more water vapor would be lost. The plant does not want this!

Experiments and Activities You Need To Know How To Describe

The Nature and Variety of Living Organisms

Structures and Functions in Living Organisms

1. Preparation of plant and animal cells (onion and cheek cells for microscope observation)
2. Osmosis in a model cell (Visking tubing – mass)
3. Osmosis in potato cells (potatoes – length)
4. Factors affecting the activity of catalase (raw/boiled/ground liver and hydrogen peroxide – height of froth)
5. What temperature does amylase work best at? (starch suspension, water baths – color of iodine solution)
6. Test for glucose (mixture of food extract and Benedict’s solution in boiling tube in hot water  bath – blue -> yellow/red)
7. Test for starch
8. Measuring the energy values of foods (holding burning food under a boiling tube of water until food is fully burnt – temperature change)

(f) Respiration

1. Respiration in animals and plants (breathing into a tube entering limewater)

(Experiments like this and variations)

(g) Gas exchange in humans

1. Effect of exercise on breathing rate http://www.curriculumonline.ie/en/Post-Primary_Curriculum/Senior_Cycle_Curriculum/Leaving_Certificate_Established/Biology/Biology_Support_Materials/Prescribed_Activities/Detailed_Templates/Investigate_the_effect_of_exercise_on_the_breathing_rate_or_pulse_rate_of_a_human.html

Transport in plants

1. Role of environmental factors in determining the rate of transpiration from a leafy shoot

• effect of wind (distance of fan) – photometer setup
• effect of light (distance of lamp – put a layer of perspex in between) – photometer setup
• effect of humidity (different-sized plastic bags around leaves) – photometer setup

 

Breathing, Respiration and Gas Exchange

1. Breathing the process of getting oxygen into the lungs and carbon dioxide out of the lungs

• Allows for gas exchange whereby oxygen is absorbed from an area of high concentration (alveoli in lungs) into an area of low concentration (red blood cells) and carbon dioxide is absorbed from an area of high concentration (blood plasma) into an area of low concentration (alveoli in lungs) by diffusion

Inhalation	Exhalation
Intercostal muscles contract	Intercostal muscles relax
…which moves ribcage up and out	….which moves ribcage down and in
Diaphragm contracts -> moves down	Diaphragm relaxes -> moves up
↑volume of thoracic cavity -> pressure -> air enters lungs to equalize pressure	volume of thoracic cavity ->↑ pressure -> air exits lungs to equalize  pressure

• Pleural membranes and pleural fluid are slippery to reduce friction during breathing movements

How are alveoli adapted for gas exchange?

Feature	Function
Thin (one cell thick)	Short diffusion distance
Large surface area	Large volumes of gas can diffuse at once
Moist	Keeps cells alive
Well ventilated (constant fresh supplies of air)	Maintains concentration gradients for oxygen and carbon dioxide
Close to a blood supply	Efficient transport of gases to/from cells

2. Respiration the process of releasing energy through the breakdown of glucose in all living cells

Aerobic respiration	Anaerobic respiration
Requires oxygen	Does not require oxygen
Glucose + oxygen -> carbon dioxide + water + energy C6H12O6 + 6O2 -> 6CO2 + 6H20 + 2900kJ/mol (kilojoules per mole of glucose)	(In plants) Glucose -> carbon dioxide + ethanol + energy (In animals) Glucose -> lactic acid + energy
Produces a lot of energy	Does not produce a lot of energy
Involves mitochondria	Does not involve mitochondria

Breathing and exercise

When we exercise…

• ↑rate of breathing
• ↑depth of breathing
• ↑heart rate

…to deliver more oxygen and glucose to the muscles faster and remove carbon dioxide 

• Before, during and after exercise, an unfit person usually has a higher pulse rate than a fit person
• After exercise, a fit person recovers much faster than an unfit person

Respiratory diseases

Chemical	What it is	Long term effect on the body
Nicotine	Highly addictive drug	Affects the CNS and brain Makes the heart beat faster Narrows blood vessels Causes heart disease Raises blood pressure Stomach ulcers Stomach cancer Lung disease
Tar	Brown substance that collects in the lungs Contains thousands of chemicals, some of which are carcinogens.	Mouth, lips, throat and lung cancer Smoker’s cough Bronchitis Pneumonia
Carbon monoxide	Poisonous gas Taken up by the blood instead of oxygen.	Reduces the body’s capacity to carry oxygen as carbon monoxide combines with haemoglobin more easily than oxygen, Deposits fats in arteries which can lead to a heart attack or stroke Poor circulation can lead to gangrene and limb amputation
Irritants and toxic substances	Chemicals	Effects the respiratory tract Causes bronchitis Poor health Reduced energy

Structure of a Villus

Epithelium only one cell thick so that there is short distance for active transport and diffusion

Goblet cell produces mucus which protects gut lining against digestion by body’s own enzymes

Capillary transports glucose (from carbohydrate breakdown) and amino acids (from protein breakdown)

Lacteal transports fatty acids and glycerol (from fat breakdown)

Gland lined with cells which produce digestive enzymes including maltase

Vein delivers absorbed products to the liver via the hepatic portal vein

Artery delivers blood to villi

Experiment proving that exhaled air contains more carbon dioxide than inhaled air

(A, B and C refer to the tubes unless specified)

Close end of B. Breathe in. Air from atmosphere enters through A, passes through limewater and enters your mouth (cannot enter through B because closed).

Open end of B and close end of A. Breathe out. Exhaled air passes through limewater in test tube B and exits through B.

Limewater in test tube B (which contained the air you exhaled) turns milky much faster than in test tube A (which contained the air you inhaled).