Module 2-4: Organisation, Evolution, and Ecosystem Dynamics Study Guide

Types of Cell Organisation

  • Unicellular Organisms

    • Definition: These consist of only a single cell.

    • Functionality: That single cell is responsible for carrying out all life processes independently.

    • Examples: Bacteria and amoebas.

  • Colonial Organisms

    • Definition: These are made up of groups of similar cells that live together in a collective group.

    • Functionality: While these cells may work together to benefit the group, they are capable of surviving independently if separated.

    • Example: Certain types of algae.

  • Multicellular Organisms

    • Definition: These are made up of many specialised cells working in coordination.

    • Functionality: Different cells perform different functions to maintain the life of the organism; individual cells typically cannot survive on their own.

    • Examples: Humans, animals, and plants.

Structure and Function of Cells, Tissues, Organs, and Organ Systems

  • Cell

    • The basic unit of life.

    • Performs specific functions required for the organism's survival.

  • Tissue

    • A group of similar cells working together to perform a specific task.

    • Example: Muscle tissue.

  • Organ

    • A group of different tissues working together to perform a complex function.

    • Examples: Heart, lungs, and the leaf of a plant.

  • Organ System

    • A group of organs working together to perform broad biological functions.

    • Examples: The digestive system and the circulatory system.

  • Organisation Hierarchy

    • Life is organized in a specific increasing order of complexity:

    • Cell→Tissue→Organ→Organ System→Organism\text{Cell} \rightarrow \text{Tissue} \rightarrow \text{Organ} \rightarrow \text{Organ System} \rightarrow \text{Organism}

How Cells Work Together to Carry Out Life Processes

  • Specialisation: Specialised cells perform specific jobs within an organism.

  • Structural Integration:

    • Cells form tissues.

    • Tissues form organs.

    • Organs form organ systems.

  • Life Maintenance: Organ systems work together in a coordinated fashion to maintain essential life processes, including respiration, digestion, and transport.

Plant Organs and Their Functions

  • Roots

    • Functions: Responsible for absorbing water and minerals from the soil and anchoring the plant firmly in the ground.

  • Stem

    • Functions: Provides structural support for the plant and acts as a transport system for water, minerals, and food.

  • Leaf

    • Functions: Serves as the primary site of photosynthesis and contains chlorophyll for capturing light energy.

  • Flower

    • Functions: Responsible for reproduction and the production of seeds.

Autotrophs vs Heterotrophs

  • Autotrophs

    • Definition: Organisms that make their own food.

    • Method: Usually through the process of photosynthesis.

    • Example: Plants.

  • Heterotrophs

    • Definition: Organisms that obtain food by consuming other organisms.

    • Example: Animals.

Photosynthesis

  • Word Equation:

    • Carbon dioxide+Water→Glucose+Oxygen\text{Carbon dioxide} + \text{Water} \rightarrow \text{Glucose} + \text{Oxygen}

  • Requirements:

    • Sunlight

    • Chlorophyll

    • Water

    • Carbon dioxide

  • Importance:

    • It produces the necessary food (glucose) for plants.

    • It releases oxygen into the atmosphere, which is vital for aerobic life.

Evolution and Species Change

  • How Species Change Over Time:

    • Species undergo gradual changes over many generations through the process of evolution.

  • Natural Selection:

    • This is the primary mechanism of evolution and occurs in four stages:

      1. Variation exists within a species.

      2. Some individuals possess traits that make them better adapted to their environment.

      3. These better-adapted individuals are more likely to survive and reproduce.

      4. Helpful traits are passed on to the next generation.

  • Adaptation:

    • Definition: A characteristic that improves an organism's chances of survival.

    • Types:

      • Structural: Physical features (e.g., thick fur in cold climates, camouflage).

      • Behavioural: Actions organisms take (e.g., nocturnal behaviour).

      • Physiological: Internal processes.

  • Specialisation for Habitats:

    • Organisms develop specific features suited to their environment:

      • Ducks possess webbed feet for swimming.

      • Cacti store water to survive in desert environments.

Relationships Between Organisms

  • Competition: Occurs when organisms compete for limited resources (food, water, space).

  • Predation: A relationship where one organism (predator) eats another organism (prey).

  • Mutualism: A relationship where both organisms benefit from the interaction.

  • Parasitism: A relationship where one organism benefits at the expense of another, which is harmed.

  • Commensalism: A relationship where one organism benefits and the other is neither helped nor harmed.

Evidence for Evolution

  • Fossils: These show the progressive changes in organisms over vast periods of time.

  • Comparative Anatomy: Similarities in body structures (homologous structures) suggest species share a common ancestry.

  • Embryology: Similarities in the development of embryos across different species point to a shared origin.

  • DNA Evidence: Similarities in DNA sequences indicate the degree of relatedness between different organisms.

Ecosystem Dynamics

  • Organism Interactions:

    • Organisms depend on each other and their physical environment for survival.

    • These interactions directly affect the survival rates and the size of populations.

  • Food Chains and Food Webs:

    • Food Chain: A diagram representing a single feeding pathway in an ecosystem.

      • Example: Grass→Rabbit→Fox\text{Grass} \rightarrow \text{Rabbit} \rightarrow \text{Fox}

    • Food Web: A complex model consisting of multiple interconnected food chains.

  • Energy Flow:

    • Energy enters the ecosystem from the Sun.

    • It is passed from producers (autotrophs) to consumers (heterotrophs).

    • Energy decreases at each trophic level (as heat or through metabolic processes).

  • Predator-Prey Relationships:

    • Predator: The organism that hunts and eats another.

    • Prey: The organism that is hunted and eaten.

    • Example: In the relationship between a fox and a rabbit, the fox is the predator and the rabbit is the prey.

    • These populations are interdependent; changes in one population directly affect the other.

Changes in Ecosystems Over Time

  • Natural Changes:

    • Environmental events such as droughts, floods, bushfires, and climate changes.

  • Ecological Succession:

    • The gradual process by which species in a particular area are replaced by a new set of species over time.

  • Human Impacts:

    • Negative Impacts: Pollution, deforestation, habitat destruction, contributing to climate change, and the introduction of invasive species.

    • Positive Impacts: Conservation programs, the establishment of national parks, habitat restoration efforts, and the promotion of recycling and sustainable practices.

Super Short Exam Definitions

  • Cell: The basic unit of life.

  • Tissue: A group of similar cells working together.

  • Organ: A group of tissues performing a specific function.

  • Organ System: A group of organs working together.

  • Autotroph: An organism that makes its own food.

  • Heterotroph: An organism that gets food from other organisms.

  • Natural Selection: The process where better-adapted organisms survive and reproduce.

  • Adaptation: A feature that improves an organism's survival.

  • Food Chain: A single pathway of energy flow.

  • Food Web: Interconnected food chains.

  • Predator: An organism that hunts another organism.

  • Prey: An organism that is hunted by a predator.