Physical activity plays a crucial role in maintaining cardiovascular health. Understanding how exercise influences heart rate is essential for students studying the Cambridge IGCSE Biology - 0610 - Supplement syllabus under the chapter 'Heart' and the unit 'Transport in Animals'. This article explores the relationship between physical activity and heart rate, providing comprehensive insights aligned with educational objectives.

Key Concepts

Understanding Heart Rate

Heart rate, measured in beats per minute (bpm), is the number of times the heart beats within a minute. It serves as an indicator of cardiac function and overall cardiovascular health. The heart rate varies based on factors such as age, fitness level, and physical activity.

Physiological Basis of Heart Rate

The heart rate is regulated by the autonomic nervous system, which comprises the sympathetic and parasympathetic nervous systems. The sympathetic nervous system increases heart rate during physical activity, preparing the body for exertion, while the parasympathetic nervous system decreases heart rate during rest to conserve energy. When engaging in physical activity, the body's demand for oxygen and nutrients increases. To meet this demand, the heart pumps blood more rapidly, resulting in an elevated heart rate. This process ensures that oxygenated blood reaches the muscles efficiently, supporting sustained physical performance.

Factors Influencing Heart Rate During Physical Activity

Several factors influence how physical activity affects heart rate:

Intensity of Exercise: Higher intensity activities, such as sprinting or heavy weightlifting, require more oxygen and nutrients, thus increasing heart rate more significantly compared to moderate or light exercises.
Fitness Level: Individuals with higher cardiovascular fitness typically have lower resting heart rates and experience smaller increases in heart rate during physical activity compared to less fit individuals.
Age: Maximum heart rate generally decreases with age. A common formula to estimate maximum heart rate is $220 - \text{age}$, which influences target heart rate zones for exercise.
Temperature and Hydration: Higher temperatures and dehydration can elevate heart rate as the body works harder to cool itself and maintain blood volume.
Health Status: Conditions such as cardiovascular diseases or respiratory issues can affect how the heart rate responds to physical activity.

The Relationship Between Physical Activity and Heart Rate

The relationship between physical activity and heart rate is direct and proportional. As physical activity intensity increases, heart rate rises to meet the heightened metabolic demands. This response is facilitated by increased sympathetic nervous system activity and decreased parasympathetic activity. During aerobic exercises like running, cycling, or swimming, the heart rate increases steadily to supply muscles with oxygen-rich blood. In contrast, anaerobic activities like sprinting lead to rapid and significant increases in heart rate due to the short-term, high-intensity nature of the exercise.

Measuring Heart Rate

Heart rate can be measured manually by palpating the pulse at various points on the body, such as the wrist (radial pulse) or neck (carotid pulse). Alternatively, electronic devices like heart rate monitors and fitness trackers provide continuous and accurate measurements during physical activity. The formula to calculate target heart rate zones for effective training is: $$\text{Target Heart Rate} = \text{Maximum Heart Rate} \times \left(\frac{\text{Desired Intensity (\%)}}{100}\right)$$ For example, for an individual aged 20 aiming for 70% intensity: $$\text{Maximum Heart Rate} = 220 - 20 = 200 \text{ bpm}$$ $$\text{Target Heart Rate} = 200 \times 0.7 = 140 \text{ bpm}$$

Adaptations to Regular Physical Activity

Regular physical activity leads to several cardiovascular adaptations that influence heart rate:

Lower Resting Heart Rate: Enhanced stroke volume allows the heart to pump more blood per beat, reducing the need for frequent beats at rest.
Improved Stroke Volume: Increased cardiac muscle strength and ventricular chamber size enable the heart to eject more blood with each contraction.
Enhanced Cardiac Efficiency: The heart becomes more efficient in oxygen utilization and blood circulation, supporting sustained physical activity with lower relative heart rates.
Reduced Sympathetic Activity: Enhanced parasympathetic tone leads to better regulation and lower heart rates during both rest and exercise.

Impact of Different Types of Physical Activity on Heart Rate

Different types of physical activity affect heart rate in varying ways:

Aerobic Exercise: Activities like jogging, swimming, and cycling elevate heart rate steadily and maintain it over extended periods. These exercises enhance cardiovascular endurance.
Anaerobic Exercise: High-intensity activities such as weightlifting and sprinting cause rapid spikes in heart rate due to short bursts of intense effort.
Isometric Exercise: Exercises involving static muscle contractions can temporarily increase heart rate, though typically less than dynamic activities.
Flexibility Exercises: Activities like yoga may have a minimal effect on heart rate but contribute to overall cardiovascular health through stress reduction and improved circulation.

Role of the Autonomic Nervous System

The autonomic nervous system (ANS) regulates involuntary physiological functions, including heart rate. The ANS consists of two primary branches:

Sympathetic Nervous System (SNS): Activates the 'fight or flight' response, increasing heart rate and cardiac output during physical activity.
Parasympathetic Nervous System (PNS): Promotes the 'rest and digest' response, slowing heart rate and conserving energy during periods of inactivity.

During exercise, the SNS predominates to meet increased metabolic demands, while the PNS facilitates recovery and lowers heart rate post-exercise.

Energy Systems and Heart Rate

The body's energy production during physical activity relies on three primary energy systems:

Phosphagen System: Provides immediate energy through the breakdown of creatine phosphate for short bursts of high-intensity activity, causing rapid heart rate increases.
Glycolytic System: Breaks down glucose for sustained high-intensity activity, maintaining elevated heart rates.
Oxidative System: Utilizes oxygen for long-term, lower-intensity activities, stabilizing heart rate at a sustained elevated level.

The utilization of these energy systems influences the magnitude and duration of heart rate responses during different types of physical activity.

Cardiovascular Drift

Cardiovascular drift refers to the gradual increase in heart rate during prolonged physical activity, especially in hot and humid conditions. Despite maintaining a steady workload, the body experiences dehydration and increased core temperature, prompting the heart to work harder to sustain blood flow and thermoregulation, resulting in an elevated heart rate over time.

Advanced Concepts

Frank-Starling Law of the Heart

The Frank-Starling Law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (end-diastolic volume) when all other factors remain constant. This intrinsic property allows the heart to adjust its force of contraction based on venous return. During physical activity, increased venous return elevates end-diastolic volume, thereby enhancing stroke volume. Consequently, the heart can pump more blood with each beat, reducing the need for excessively high heart rates to meet the body's demands. $$ \text{Stroke Volume (SV)} = \text{End-Diastolic Volume (EDV)} - \text{End-Systolic Volume (ESV)} $$

Cardiac Output and Its Regulation

Cardiac output (CO) is the volume of blood the heart pumps per minute and is a product of heart rate (HR) and stroke volume (SV): $$ \text{CO} = \text{HR} \times \text{SV} $$ Regulation of cardiac output is vital during physical activity to ensure adequate oxygen delivery to tissues. During exercise, both HR and SV increase to elevate CO, but the extent of each depends on the intensity and duration of the activity as well as the individual's fitness level.

Baroreceptor Reflex

Baroreceptors are stretch-sensitive receptors located in the carotid sinus and aortic arch. They detect changes in blood pressure and relay this information to the central nervous system. During physical activity, baroreceptors help regulate HR and blood vessel dilation to maintain stable blood pressure despite increased CO.

Chemoreceptor Reflex

Chemoreceptors respond to changes in blood chemistry, such as increased carbon dioxide (CO₂) levels and decreased pH during exercise. These receptors stimulate increased ventilation and HR to enhance CO₂ removal and oxygen delivery.

Mathematical Modeling of Heart Rate Responses

Mathematical models can predict heart rate responses to different levels of physical activity. One such model considers the linear relationship between exercise intensity and HR: $$ \text{HR} = \text{HR}_{\text{rest}} + (\text{Intensity} \times \Delta \text{HR}) $$ Where:

HR_rest: Resting heart rate
Intensity: Percentage of maximum exercise capacity
ΔHR: Heart rate increase per unit of intensity

This model helps in designing exercise programs by estimating the expected HR at various intensity levels, ensuring exercises are performed within safe and effective HR zones.

Impact of Chronic Physical Activity on Heart Remodeling

Chronic physical activity induces structural changes in the heart, known as heart remodeling. These adaptations include:

Left Ventricular Hypertrophy: Enlargement of the left ventricle increases stroke volume and cardiac output, enhancing endurance.
Increased Capillarization: More capillaries per muscle fiber improve oxygen delivery and waste removal.
Enhanced Mitochondrial Density: Greater mitochondrial content in cardiac and skeletal muscles boosts aerobic metabolism efficiency.

These structural changes contribute to lower resting heart rates and improved performance during physical activity.

Interdisciplinary Connections: Exercise Physiology and Biomedical Engineering

Understanding the effect of physical activity on heart rate bridges multiple disciplines:

Exercise Physiology: Studies the body's acute responses and chronic adaptations to physical activity, focusing on cardiovascular, respiratory, and muscular systems.
Biomedical Engineering: Develops devices like heart rate monitors and biofeedback systems that track and analyze heart rate data to optimize training and health.
Sports Medicine: Integrates knowledge of heart rate dynamics to prevent injuries, enhance performance, and manage cardiac conditions in athletes.
Public Health: Utilizes heart rate data to design effective exercise guidelines and promote cardiovascular health in populations.

Advanced Problem-Solving: Calculating Target Heart Rate Zones

Consider a 25-year-old individual planning an exercise regimen. To determine their target heart rate zone for moderate-intensity exercise (60-70% of maximum heart rate), apply the following steps:

Calculate Maximum Heart Rate (MHR): $$\text{MHR} = 220 - \text{age} = 220 - 25 = 195 \text{ bpm}$$
Determine Target HR Range:
- Lower end (60%): $$195 \times 0.6 = 117 \text{ bpm}$$
- Upper end (70%): $$195 \times 0.7 = 136.5 \text{ bpm}$$
Target Heart Rate Zone: 117 bpm to 136.5 bpm

This calculation ensures the exercise intensity is sufficient to improve cardiovascular fitness without overexertion.

Experimental Techniques to Study Heart Rate Responses

Researchers employ various experimental methods to study how physical activity affects heart rate:

Treadmill Stress Test: Measures HR responses to incremental exercise intensities, assessing cardiovascular endurance and detecting abnormalities.
Electrocardiography (ECG): Records the electrical activity of the heart, providing detailed insights into HR variability and rhythm during and after exercise.
Heart Rate Variability (HRV) Analysis: Evaluates autonomic nervous system function by assessing variations in time intervals between heartbeats.
Wearable Technology: Utilizes sensors in fitness trackers and smartwatches to monitor real-time HR data during daily activities and structured exercises.

Pharmacological Influences on Heart Rate During Exercise

Certain medications can alter heart rate responses to physical activity:

Beta-Blockers: Reduce heart rate and cardiac output by inhibiting sympathetic nervous system activity, often prescribed for hypertension and arrhythmias.
Stimulants: Increase heart rate by enhancing sympathetic activity, sometimes used for attention deficit disorders but can pose risks during intense exercise.
Diuretics: May indirectly affect heart rate by altering blood volume and electrolyte balance.

Understanding these pharmacological effects is crucial for managing exercise programs in individuals taking these medications.

Impact of High Altitude on Heart Rate During Physical Activity

At high altitudes, reduced atmospheric oxygen levels (hypoxia) challenge the cardiovascular system. To compensate, heart rate increases during physical activity to enhance oxygen delivery to tissues. Prolonged exposure can lead to physiological adaptations, such as increased red blood cell production, to improve oxygen-carrying capacity and stabilize heart rate responses. $$ \text{Oxygen Delivery} = \text{Cardiac Output} \times \text{Arterial Oxygen Content} $$ With decreased oxygen availability, maintaining oxygen delivery necessitates elevated cardiac output, achieved through increased heart rate and stroke volume.

Genetic Factors Influencing Heart Rate Responses

Genetic variations can influence how individuals' heart rates respond to physical activity:

Adrenergic Receptor Genes: Variants in these genes affect the responsiveness of the heart to adrenaline and noradrenaline, altering HR responses to exercise.
Beta-1 Adrenergic Receptor Polymorphisms: Influence heart rate variability and resting HR, impacting cardiovascular fitness and exercise tolerance.
Angiotensin-Converting Enzyme (ACE) Genes: Associated with differences in cardiac structure and function, affecting stroke volume and heart rate dynamics.

Understanding genetic predispositions can aid in personalized exercise programs and cardiovascular risk assessment.

Comparison Table

Aspect	Aerobic Exercise	Anaerobic Exercise
Definition	Continuous, rhythmic activities that improve cardiovascular endurance.	Short bursts of high-intensity effort to build strength and power.
Heart Rate Response	Gradual increase and sustained elevated heart rate.	Rapid spike in heart rate during exertion.
Primary Energy System	Oxidative system using oxygen for energy production.	Phosphagen and glycolytic systems utilizing stored energy without oxygen.
Benefits	Improves cardiovascular endurance, lowers resting heart rate.	Enhances muscle strength, increases power and speed.
Examples	Running, swimming, cycling.	Sprinting, heavy weightlifting, high-intensity interval training (HIIT).

Summary and Key Takeaways

Physical activity directly influences heart rate, increasing it to meet the body's heightened demands.
Regular exercise leads to cardiovascular adaptations, enhancing heart efficiency and lowering resting heart rate.
Different exercise types affect heart rate uniquely, with aerobic and anaerobic activities eliciting varying responses.
Understanding heart rate dynamics is essential for optimizing exercise programs and promoting cardiovascular health.

Examiner Tip

Tips

To effectively monitor your heart rate during exercise, use the "talk test"—if you can maintain a conversation, you're likely in the moderate-intensity zone. Remember the mnemonic F.I.T.T.: Frequency, Intensity, Time, and Type, to structure your workouts optimally. Additionally, familiarize yourself with the formula for target heart rate: 220 minus your age, then multiply by your desired intensity percentage. Regularly tracking your heart rate can help you gauge progress and adjust your training for better cardiovascular health.

Did You Know

Did you know that elite athletes often have resting heart rates as low as 40 bpm, compared to the average 60-100 bpm in non-athletes? This is due to their hearts becoming more efficient through rigorous training. Additionally, studies have shown that regular physical activity can help prevent tachycardia, a condition where the heart beats excessively fast, thereby reducing the risk of heart-related complications.

Common Mistakes

One common mistake students make is confusing maximum heart rate with target heart rate zones. Remember, the maximum heart rate ($220 - \text{age}$) is different from the range you should aim for during exercise. Another frequent error is neglecting to account for factors like hydration and temperature, which can significantly impact heart rate responses. Finally, some students incorrectly assume that a higher heart rate always means a better workout, overlooking the importance of maintaining appropriate intensity levels for individual fitness goals.

FAQ

What is a normal resting heart rate?

A normal resting heart rate for adults ranges from 60 to 100 beats per minute (bpm).

How does age affect maximum heart rate?

Maximum heart rate generally decreases with age and can be estimated using the formula $220 - \text{age}$.

Why is heart rate important during exercise?

Heart rate indicates the intensity of your workout and helps ensure you are exercising within safe and effective zones to improve cardiovascular health.

Can overtraining affect heart rate?

Yes, overtraining can lead to elevated resting heart rate and reduced heart rate variability, indicating insufficient recovery.

How does hydration influence heart rate?

Dehydration can cause an increase in heart rate as the body works harder to maintain blood flow and temperature regulation.

What are the benefits of a lower resting heart rate?

A lower resting heart rate typically indicates a more efficient heart function and better cardiovascular fitness.

1. Transport in Animals

1.1 Blood

1.1.1 Identify lymphocytes and phagocytes in diagrams

1.1.2 Lymphocytes produce antibodies

1.1.3 Phagocytes engulf pathogens by phagocytosis

1.1.4 Clotting: fibrinogen converts to fibrin to form mesh

1.2 Circulatory Systems

1.2.1 Single circulation in fish

1.2.2 Double circulation in mammals

1.2.3 Advantages of double circulation

1.3 Heart

1.3.1 Identify atrioventricular and semilunar valves

1.3.2 Left ventricle has thicker walls than right ventricle

1.3.3 Atria walls thinner than ventricles

1.3.4 Importance of septum in separating oxygenated and deoxygenated blood

1.3.5 Effect of physical activity on heart rate

1.3.6 Heart function: atria and ventricles contracting, valve action

1.4 Blood Vessels

1.4.1 Artery and vein structure linked to blood pressure

1.4.2 Capillary structure linked to function

1.4.3 Identify hepatic artery, hepatic veins, and hepatic portal vein

2. Reproduction

2.1 Sexual Reproduction in Humans

2.1.1 Function of placenta and umbilical cord in nutrient, gas, and waste exchange

2.1.2 Pathogens and toxins can cross the placenta

2.2 Sex Hormones in Humans

2.2.1 Sites of oestrogen and progesterone production in menstrual cycle and pregnancy

2.2.2 Roles of FSH, LH, progesterone, and oestrogen in menstrual cycle and pregnancy

2.3 Asexual Reproduction

2.3.1 Advantages and disadvantages of asexual reproduction in nature and crops

2.4 Sexual Reproduction

2.4.1 Advantages and disadvantages of sexual reproduction in nature and crops

2.4.2 Haploid gametes and diploid zygote formation

2.5 Sexual Reproduction in Plants

2.5.1 Self-pollination: pollen transfer within the same plant

2.5.2 Cross-pollination: pollen transfer between plants

2.5.3 Effects of self- vs cross-pollination on variation and reliance on pollinators

2.5.4 Pollen tube growth, ovule entry, and fertilization

3. Organisms and Their Environment

3.1 Populations

3.1.1 Factors affecting sigmoid population growth curve

3.2 Food Chains and Food Webs

3.2.1 Draw, describe, and interpret pyramids of energy

3.2.2 Advantages of pyramids of energy over pyramids of numbers or biomass

3.2.3 Energy transfer between trophic levels is inefficient

3.2.4 Humans gain more energy eating crops than livestock

3.2.5 Food chains usually have fewer than five trophic levels

3.3 Nutrient Cycles

3.3.1 Nitrogen cycle: decomposition, nitrification, nitrogen fixation, denitrification

3.3.2 Microorganisms in nitrogen cycle: decomposition, nitrification, nitrogen fixation, denitrification

4. Biological Molecules

4.1 DNA Structure

4.1.1 Base pairing: A with T, C with G

4.1.2 DNA has two strands coiled in a double helix

4.1.3 Each strand contains bases

4.1.4 Base pairs hold DNA strands together

5. Excretion in Humans

5.1 Liver Function

5.1.1 Liver converts amino acids to proteins

5.1.2 Urea is formed from excess amino acids

5.1.3 Deamination: removal of nitrogen-containing part of amino acids to form urea

5.2 Importance of Excretion

5.2.1 Excretion prevents urea toxicity

5.3 Kidney Structure

5.3.1 Identify cortex and medulla in kidney diagrams

5.4 Nephron Function

5.4.1 Role of glomerulus in filtration of water, glucose, urea, and ions

5.4.2 Nephron reabsorbs glucose, some ions, and most water

5.4.3 Urine contains urea, excess water, and excess ions

6. Human Influences on Ecosystems

6.1 Food Supply

6.1.1 Social, environmental, and economic issues in feeding a growing population

6.1.2 Need for sustainable food production

6.1.3 Causes of famine: unequal food distribution, drought, floods, population growth, poverty

6.2 Pollution

6.2.1 Eutrophication: nitrate increase, algae growth, oxygen depletion, aquatic life loss

6.2.2 Impact of female contraceptive hormones on aquatic organisms and sperm count

6.2.3 Formation and effects of acid rain on ecosystems

6.2.4 Deforestation effects: species extinction, soil erosion, flooding, increased CO₂

6.3 Conservation

6.3.1 Low population size risks: reduced genetic variation, limited adaptation to change

7. Enzymes

7.1 Enzyme Action

7.1.1 Define active site, enzyme-substrate complex, substrate, product

7.1.2 Enzyme specificity due to active site shape

7.1.3 Effect of temperature on enzyme activity: kinetic energy, collisions, denaturation

7.1.4 Effect of pH on enzyme activity: shape, fit, denaturation

8. Inheritance

8.1 Chromosomes, Genes, and Proteins

8.1.1 DNA base sequence determines amino acid sequence in proteins

8.1.2 Different amino acid sequences create different protein shapes

8.1.3 DNA controls cell function by coding for proteins

8.1.4 Protein synthesis: mRNA copies gene, ribosome assembles amino acids

8.1.5 Genes in a cell are selectively expressed for specific functions

8.1.6 Haploid nucleus: one set of chromosomes

8.1.7 Diploid nucleus: two sets of chromosomes

8.1.8 Human diploid cells have 23 chromosome pairs

8.2 Monohybrid Inheritance

8.2.1 Test cross used to determine an unknown genotype

8.2.2 Codominance: both alleles contribute to phenotype

8.2.3 ABO blood group inheritance: A, B, AB, O alleles

8.2.4 Sex-linked characteristics: gene located on sex chromosome

8.2.5 Red-green color blindness as a sex-linked trait

8.2.6 Use genetic diagrams to predict codominance and sex-linked inheritance

9. Diseases and Immunity

9.1 Immune System

9.1.1 Active immunity: body produces antibodies

9.1.2 Pathogens have unique antigens

9.1.3 Antibodies bind to antigens to destroy or mark pathogens

9.1.4 Antibodies have complementary shapes to specific antigens

9.1.5 Active immunity from infection or vaccination

9.2 Vaccination

9.2.1 Process of vaccination: weakened pathogens or antigens stimulate antibody production

9.2.2 Memory cells provide long-term immunity

9.2.3 Role of vaccination in disease control

9.3 Passive Immunity

9.3.1 Short-term defense by receiving antibodies from another source

9.3.2 Passive immunity via placenta or breast milk

9.3.3 No memory cells produced in passive immunity

10. Coordination and Response

10.1 Synapses

10.1.1 Structure of a synapse: vesicles, synaptic gap, receptor proteins

10.1.2 Events at a synapse: neurotransmitter release, diffusion, binding, impulse transmission

10.1.3 Synapses ensure one-way transmission of impulses

10.2 Sense Organs

10.2.1 Pupil reflex: antagonistic action of circular and radial muscles

10.2.2 Accommodation: ciliary muscles, suspensory ligaments, lens shape

10.2.3 Distribution of rods and cones in the retina

10.2.4 Function of rods (night vision) and cones (color vision)

10.2.5 Identify the fovea and state its function

10.3 Hormones

10.3.1 Glucagon secretion by the pancreas

10.3.2 Adrenaline increases blood glucose and heart rate

10.4 Homeostasis

10.4.1 Negative feedback maintains stable internal conditions

10.4.2 Blood glucose regulation by insulin and glucagon

10.4.3 Type 1 diabetes: causes and treatment

10.4.4 Identify skin structures: hairs, sweat glands, receptors, blood vessels

10.4.5 Regulating body temperature: insulation, sweating, shivering

10.4.6 Vasodilation and vasoconstriction regulate heat loss

10.5 Tropic Responses

10.5.1 Phototropism and gravitropism as chemical control in plants

10.5.2 Auxin controls shoot growth: production, diffusion, response to stimuli

11. Plant Nutrition

11.1 Photosynthesis

11.1.1 Balanced equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

11.1.2 Identify and explain limiting factors in photosynthesis

12. Human Nutrition

12.1 Digestive System

12.1.1 Bile emulsifies fats to increase surface area

12.2 Chemical Digestion

12.2.1 Starch digestion: amylase → maltose, maltase → glucose

12.2.2 Protein digestion: pepsin (stomach), trypsin (small intestine)

12.2.3 Bile neutralizes stomach acid for enzyme activity

12.3 Absorption

12.3.1 Villi and microvilli increase surface area for absorption

12.3.2 Structure of a villus

12.3.3 Role of capillaries and lacteals in absorption

13. Biotechnology and Genetic Modification

13.1 Biotechnology

13.1.1 Role of *Penicillium* in penicillin production

13.2 Genetic Modification

13.2.1 Genetic modification process: restriction enzymes, plasmids, recombinant DNA

13.2.2 Insertion of recombinant plasmids into bacteria for protein production

13.2.3 Advantages and disadvantages of genetically modified crops

13.2.4 GM crops: increased yield, pest resistance, herbicide resistance, ecological risks

14. Transport in Plants

14.1 Xylem and Phloem

14.1.1 Xylem structure: thick lignified walls, no cell contents, continuous tubes

14.2 Transpiration

14.2.1 Water loss related to air spaces, stomata size and number

14.2.2 Water moves up xylem via transpiration pull and cohesion

14.2.3 Factors affecting transpiration: temperature, wind speed, humidity

14.2.4 How and why wilting occurs

15. Characteristics and Classification of Living Organisms

15.1 Classification Systems

15.1.1 Classification reflects evolutionary relationships

15.1.2 DNA base sequences used for classification

15.1.3 More closely related organisms have similar DNA sequences

15.2 Features of Organisms

15.2.1 Five kingdoms: animal, plant, fungus, prokaryote, protoctist

15.2.2 Plant kingdom: ferns and flowering plants (monocots, dicots)

15.2.3 Classify organisms using kingdom and plant group features

15.2.4 Features of viruses: protein coat, genetic material

16. Variation and Selection

16.1 Variation

16.1.1 Gene mutation: random DNA base sequence change

16.1.2 Sources of genetic variation: mutation, meiosis, random fertilization

16.2 Adaptive Features

16.2.1 Adaptations of hydrophytes and xerophytes to their environments

16.3 Selection

16.3.1 Adaptation via natural selection over generations

16.3.2 Antibiotic-resistant bacteria as an example of natural selection

16.3.3 Difference between natural and artificial selection

17. Gas Exchange in Humans

17.1 Gas Exchange System

17.1.1 Identify internal and external intercostal muscles

17.1.2 Function of cartilage in the trachea

17.1.3 Role of ribs, intercostal muscles, and diaphragm in ventilation

17.1.4 Difference between inspired and expired air composition

17.1.5 Effect of physical activity on breathing rate and depth

17.1.6 Role of goblet cells, mucus, and ciliated cells in protecting the respiratory system

18. Organisation of the Organism

18.1 Size of Specimens

18.1.1 Convert between millimetres (mm) and micrometres (μm)

19. Movement into and out of Cells

19.1 Osmosis

19.1.1 Define osmosis in terms of water potential and membranes

19.1.2 Effects of different solutions on plant cells: turgid, turgor pressure, plasmolysis, flaccid

19.1.3 Importance of osmosis in water uptake and loss in organisms

19.2 Active Transport

19.2.1 Protein carriers move molecules across membranes

19.2.2 Importance of active transport (e.g., ion uptake in roots)

20. Drugs

20.1 Antibiotics

20.1.1 Using antibiotics only when essential limits bacterial resistance

20.1.2 MRSA as an example of antibiotic-resistant bacteria

21. Respiration

21.1 Aerobic Respiration

21.1.1 Balanced equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

21.2 Anaerobic Respiration

21.2.1 Lactic acid builds up during vigorous exercise

21.2.2 Oxygen debt: heart rate remains high to transport lactic acid

21.2.3 Oxygen debt: deeper, faster breathing removes lactic acid

21.2.4 Lactic acid aerobically broken down in the liver

21.2.5 Balanced equation in yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

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Effect of Physical Activity on Heart Rate

Introduction