Comprehensive Study Notes on Life Processes and Biological Organisation and Genetics

Introduction to Biology and the Seven Life Processes

• Biology is the scientific study of living things.

• To be classified as living, an organism must carry out the seven life processes, often remembered by the mnemonic MRS GREN.

The Seven Life Processes (MRS GREN)

• Move / Movement: Changing position. This can include movement of the whole body or specific parts like leaves.

• Respire / Respiration: Releasing energy from food. This is a chemical process occurring within cells.

• Sense / Sensitivity: Noticing and responding to surroundings or stimuli.

• Grow / Growth: An increase in size.

• Reproduce / Reproduction: Producing offspring or babies.

• Excrete / Excretion: Getting rid of waste products produced by cells.

• Nutrition: Making or getting food to obtain energy and nutrients.

MRS C GREN

• An updated version of the mnemonic is MRS C GREN, where the C stands for Cells.

• Cells are defined as the smallest, fully-functioning units of life. All living things are made up of one or more cells, and these cells carry out the seven life processes.

Application of Life Processes to Organisms and Non-Living Things

• Strawberry Plant (Living):

  • Move: Leaves follow the sun.

  • Respire: They take in oxygen to release energy from food.

  • Sense: Roots grow towards water.

  • Grow: They get taller and wider.

  • Reproduce: They make seeds or send out runners.

  • Excrete: They release oxygen into the air.

  • Nutrition: They make their own food via photosynthesis.

• Cat (Living):

  • Move: Muscles contract and relax to allow jumping.

  • Respire: Oxygen is taken in to release energy from food.

  • Sense: They use smell to detect and attack other cats.

  • Grow: They grow longer and wider.

  • Reproduce: They have kittens.

  • Excrete: They sweat.

  • Nutrition: They catch and eat mice.

• Bacterium (Living):

  • Move: They wiggle a flagellum (a whip-like tail) for locomotion.

  • Respire: They take in oxygen to release energy from food.

  • Sense: They can detect a single drop of a chemical in a pool of $1,000$ drops.

  • Grow: They increase in size before reproducing.

  • Reproduce: They split in half.

  • Excrete: They release lactic acid.

  • Nutrition: They secrete digestive enzymes onto food to break it down before absorption.

• Fire (Non-Living):

  • Fire may appear to move (flickering), respire (taking in oxygen), sense (moving away from water), grow (from spark to inferno), reproduce (sparks starting new fires), excrete (releasing $CO_2$), and consume nutrition (wood).

  • However, fire is not living because it is not made up of cells.

Degrees of Living Status

• Living: Made up of cells and currently performing the seven life processes.

• Dormant ("Will Live"): Made up of cells and has the potential to do all seven life processes.

• Dead ("Was Living"): Made up of cells but used to do the seven life processes and no longer does.

• Non-Living ("Never Living"): Not made up of cells and cannot carry out the life processes.

Key Biological Distinctions

• Respiration ≠ Breathing: Respiration is the intracellular process of releasing energy from food. Breathing is the physical mechanism of bringing oxygenated air into lungs and removing deoxygenated air.

• Excretion ≠ Pooping: Excretion is the removal of metabolic wastes produced by cells. Pooping (egestion) is the removal of undigested food that was never absorbed into the body.

Cellular Structure and Organelles

Basic Definitions

• Cell: The basic building block of life; the smallest fully-functioning unit.

• Organelle: A specialized part of a cell that performs a specific function.

Comparative Anatomy: Plant vs. Animal Cells

• Shared Organelles:

  • Cell Membrane: Controls the entry and exit of substances into and out of the cell.

  • DNA: Contains the instructions to make proteins that form the structure or carry out the functions of the cell.

  • Nucleus: Contains the DNA for cell processes and replication; controls cell function.

  • Mitochondria: Carries out the life process of respiration to provide energy.

  • Cytoplasm: A jelly-like substance that supports organelles and provides space for biological reactions.

• Plant-Specific Organelles:

  • Cell Wall: Provides rigid structure to the cell.

  • Large Central Vacuole: Stores water and provides structural support (turgor pressure).

  • Chloroplasts: Organelles that carry out photosynthesis to produce food.

Specialized Cells and Their Adaptations

• In complex organisms, cells are specialized with specific features to perform their jobs effectively.

Examples of Specialized Cells

• Root Hair Cell: Function is to absorb water and minerals from the soil. Structure: Long thin extensions to increase surface area for efficiency.

• Sperm Cell: Function is to fertilize an egg cell. Structure: Has a tail for swimming and extra mitochondria to provide energy for movement.

• Neuron (Nerve Cell): Function is to carry nerve signals around the body. Structure: Very long so signals can be carried quickly.

• Epidermis Cell: Function is to protect the inside of a leaf. Structure: Transparent to allow sunlight through; no chloroplasts; produces a waxy cuticle to prevent water loss.

• Palisade Mesophyll Cell: Main site of photosynthesis. Structure: Regular shape for tight packing; contains a high number of chloroplasts.

• Red Blood Cell: Function is to transport oxygen. Structure: No nucleus to increase surface area for oxygen carrying.

• Muscle Cell: Function is to contract and relax for movement. Structure: Made of filaments that slide over each other.

• White Blood Cell: Function is to protect against pathogens. Structure: Can change shape to engulf pathogens.

• Bone Cell: Function is to support the body. Structure: Contains calcium to make them hard.

• Spongy Mesophyll Cell: Back-up site for photosynthesis. Structure: Round shape with air spaces to allow gas movement.

• Guard Cell: Function is to open and close stomata (pores for gas exchange). Structure: Able to expand and contract.

Levels of Biological Organization

• Organisms are organized into a hierarchy of increasing complexity:

1. Cell: The basic building block of life.

2. Tissue: A group of similar cells working together to carry out a particular function (e.g., Cardiac Tissue, Smooth Muscle Cell).

3. Organ: A group of different tissues working together to perform a function (e.g., Heart).

4. Organ System: A group of organs working together for a specific function (e.g., Circulatory System).

5. Organism: A whole living thing made of multiple organ systems (e.g., Human).

The 11 Human Organ Systems

• Integumentary, Muscular, Skeletal, Nervous, Circulatory, Respiratory, Endocrine, Urinary/Excretory, Reproductive, Digestive, and Lymphatic/Immune.

Higher Levels of Organization

• Population: A group of individuals of the same species.

• Community: Multiple populations interacting.

• Ecosystem: Communities interacting with들의 abiotic (non-living) environment.

• Biome: A regional ecosystem.

• Biosphere: The global sum of all ecosystems.

Genetics and Inheritance

Key Definitions

• DNA (Deoxyribonucleic Acid): The molecule containing genetic information and instructions to make proteins.

• Chromosome: A long strand of DNA wrapped around histones that contains many genes. Human body cells contain $46$ chromosomes ($23$ homologous pairs).

• Gene: A section of DNA/chromosome that codes for a specific trait or characteristic.

• Allele: An alternate version of a gene (e.g., brown fur allele vs. ginger fur allele).

• Variation: The differences between individuals of the same species.

DNA Structure

• DNA is a Double Helix, resembling a twisted ladder.

• Rails/Backbone: Alternating sugar and phosphate groups.

• Rungs: Complementary base pairs.

• Nucleotides: The building blocks of DNA, consisting of a phosphate, a sugar (deoxyribose), and a base.

• Nitrogenous Bases:

  • Adenine ($A$) pairs with Thymine ($T$).

  • Cytosine ($C$) pairs with Guanine ($G$).

Protein Synthesis and Function

• DNA provides instructions for two types of proteins:

  • Structural Proteins: e.g., Keratin (hair/nails), Collagen (skin/bones), Actin and Myosin (muscle contraction).

  • Functional Proteins: e.g., Salivary Amylase (enzyme), Insulin (hormone for glucose uptake), Human Growth Hormone ($hGH$).

Causes of Variation

1. Inherited Factors: Features passed from parents via DNA (e.g., natural hair color).

2. Environmental Factors: Features affected by surroundings (e.g., hair getting lighter in the sun).

   • Traits can be Discrete (categories) or Continuous (ranges).

Natural Selection and Adaptation

Natural Selection

• Natural selection is the process where individuals with advantageous alleles (DNA) survive environmental factors (selection pressure) to reproduce and pass on their DNA to offspring.

• The Process:

  1. Variation: Within a population, variation exists due to mutations in genes.

  2. Selection Pressure: A factor like a predator or environmental change makes survival difficult.

  3. Survival of the Fittest: Individuals with favorable traits are better camouflaged or equipped to survive.

  4. Reproduction: Survivors reproduce and pass on their alleles.

  5. Generational Change: Over many generations, the frequency of favorable alleles increases in the population.

• Example (Frogs): If dark and light green frogs live on a dark log, predators (birds) will eat the light green ones. The dark green frogs survive and reproduce, leading to a darker population over time.

• Importance of Variation: It prevents extinction. If the environment changes, variation ensures some individuals might have alleles to survive.

Adaptations

• An Adaptation is an inherited feature that allows an organism to survive and reproduce in its habitat.

• Types of Adaptations:

  • Structural: Physical features of the body (e.g., a Kiwi's whiskers, a tiger's large teeth/stripes).

  • Behavioural: Ways an organism acts (e.g., Kiwi being nocturnal, a tiger stalking prey).

  • Physiological: Internal processes/chemistry (e.g., a Kiwi's highly developed sense of smell, a tiger's digestive enzymes).

Plant Reproduction and Life Cycle

Flower Anatomy and Function

• Male Parts (Stamen):

  • Anther: Where pollen is produced.

  • Filament: The stem support for the anther.

• Female Parts (Carpel/Pistil):

  • Stigma: Sticky landing platform for pollen.

  • Style: The tube the pollen grain descends through.

  • Ovary: Contains the female gametes (ovules).

• Other Parts:

  • Petal: Brightly colored to attract pollinators.

  • Sepal: Protects the flower bud.

The Life Cycle of a Flowering Plant

1. Meiosis: Occurs in the anther and ovary to produce haploid ($n$) sex cells (pollen and ovules).

2. Pollination: The transfer of pollen from the anther to the stigma by wind, water, or pollinators (insects/animals).

3. Fertilisation: The pollen grain grows a pollen tube down the style to the ovary. One sperm nucleus joins with the egg nucleus to form a diploid ($2n$) zygote.

4. Seed and Fruit Formation: After fertilization, the petals fall off and the ovary swells (via mitosis) to become a fruit containing seeds.

5. Seed Dispersal: Moving seeds away from the parent plant via wind, animals, water, humans, or bursting.

6. Germination: The seed turns into a plant using warmth and water.

7. Growth: Occurs through mitosis, creating new body cells ($2n$).

Mammal Reproduction and Life Cycle

Male Reproductive Anatomy

• Testes: Produce sperm and testosterone.

• Scrotum: Sac holding the testes.

• Epididymis: Stores sperm.

• Vas Deferens (Sperm Duct): Connects epididymis to the urethra.

• Prostate: Adds nutrient-rich fluid to sperm.

• Urethra: Tube for urine and semen passage.

• Penis: External sex organ.

Female Reproductive Anatomy

• Ovary: Contains eggs.

• Fallopian Tube: Connects ovary to uterus; site of fertilisation.

• Uterus: Where the baby/fetus develops.

• Cervix: Junction between uterus and vagina.

• Vagina: Muscular tube connecting to the vulva.

The Mammal Life Cycle

1. Meiosis: Occurs in sex organs to halve the chromosome number from $46$ ($23$ pairs) to $23$ in gametes (sperm and egg). Gametes are haploid ($n$).

2. Fertilisation: A sperm nucleus enters and joins the egg nucleus in the Fallopian tube, forming a zygote with $46$ chromosomes. The zygote is diploid ($2n$).

3. Implantation and Growth: The zygote moves to the uterus and becomes an embryo (a ball of identical cells) through mitosis (cell division for growth).

4. Differentiation: Cells become specialized (e.g., heart, bone) as the embryo develops into a foetus and eventually a baby.

5. Birth and Postnatal Growth: The baby grows into an adult through continuous mitosis.

Questions & Discussion

• What does MRS GREN stand for?

  • It stands for Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.

• Is a strawberry plant living? Why?

  • Yes, it carries out all seven life processes, such as making food via photosynthesis and moving leaves to follow the sun.

• Is fire living? Why not?

  • No. While it shares some characteristics with living things, it is not composed of cells, which is a fundamental requirement for life.

• What is the difference between haploid and diploid?

  • Haploid ($n$) means having half the number of chromosomes ($23$ in humans), while diploid ($2n$) means having the full set ($46$ in humans).

• How does the root hair cell structure relate to its function?

  • It has long thin extensions to increase the surface area, allowing it to absorb water and minerals more efficiently.

• Why is variation important if the environment changes?

  • Variation ensures that some individuals may have alleles that allow survival in new conditions, preventing the extinction of the entire species.