The Earth System

1. The Biosphere:

   • The biosphere is the part of Earth where all living organisms reside and interact.

   • Within the biosphere, smaller subsystems of organisms exist in both aquatic and terrestrial environments.

2. Matter and Energy in the Earth System:

   • Earth is a closed system for matter, meaning matter largely remains within the system.

   • Earth is an open system for energy, as it receives energy from the sun, which drives processes within the system.

   • Light Energy Transformation: Sunlight energy enters the Earth system, where it can be transformed into heat, which impacts climate, water cycle, and other Earth processes.

3. Spheres of the Earth System:

   • Geosphere: The solid features of Earth, like rocks and soil.

   • Hydrosphere: All water bodies, including oceans, lakes, and rivers.

   • Biosphere: The area where life exists, encompassing all ecosystems.

   • Atmosphere: The layer of gases surrounding Earth.

   • Anthrosphere: The part of Earth’s environment modified by human activities.

Organization of the Biosphere

1. Ecosystems:

   • Ecosystems consist of biotic (living) and abiotic (non-living) components.

   • Biotic and abiotic components interact, cycling energy and matter through the ecosystem.

   • Ecosystems have feedback mechanisms to help them recover from changes or disturbances.

2. Ecological Hierarchies:

   • Population: A group of individuals from the same species in a specific area.

   • Community: Multiple populations of different species coexisting in an area.

   • Ecosystem Types: Land-based, air-based, and water-based ecosystems exist, each with unique biotic and abiotic components.

3. Biomes:

   • Biomes are large ecological areas with specific climates and communities, including aquatic (saltwater and freshwater) and terrestrial types.

   • Each biome has adapted plant and animal species, which interact with each other and their environments.

Characteristics of Living Things

1. Life Processes:

   • All living organisms require energy, grow, and reproduce.

   • They respond to environmental changes, maintaining internal stability through homeostasis.

   • Homeostasis: Organisms maintain stable internal conditions despite external changes, essential for survival.

2. Viruses:

   • Viruses are not considered living as they lack cells, cannot perform homeostasis, and rely on a host for reproduction.

   • They consist of genetic material within a protein coat and do not perform independent metabolic functions.

Interactions in Ecosystems

1. Ecosystem Structure:

   • An ecosystem functions as a system with defined boundaries, components, inputs, and outputs.

   • Organisms require specific resources and conditions to thrive within their habitats.

2. Habitat and Niche:

   • Habitat: The environment where an organism lives, encompassing biotic and abiotic factors.

   • Niche: The specific role or function of an organism in its environment, including its resource needs, behaviors, and interactions with other organisms.

3. Relationships:

   • Predation: One organism (predator) hunts and consumes another (prey), essential in energy transfer.

   • Competition: Organisms compete for resources like space, food, and water.

• Symbiosis:

  • Mutualism: Both species benefit.

  • Parasitism: One species benefits, and the other is harmed.

  • Commensalism: One species benefits, while the other is unaffected.

Biodiversity

1. Importance of Biodiversity:

   • Higher biodiversity contributes to ecosystem resilience, allowing for quicker recovery from disturbances like pollution.

   • Biodiversity refers to the variety of species within a specific area.

2. Measuring Biodiversity:

   • Species Richness: The count of different species within a unit area.

   • Species Evenness: The relative population sizes of different species within an area, reflecting the balance of species distribution.

Study guide

• Atoms, Elements, and Compounds

• Chemical Reactions

• Properties of Carbon

• Carbohydrate Structure and Function

• Chemical Energy and ATP

• Matter and Energy in Photosynthesis

  • Inputs and Outputs of Photosynthesis

  • Light and Photosynthesis

  • Photosynthesis and Earth's Atmosphere

• Transforming Light Energy

  • Stages of Photosynthesis

Atoms, Elements, and Compounds

• Atoms: The smallest basic unit of matter; consists of protons (+), neutrons (0), and electrons (-).

• Elements: Composed of one type of atom, defined by the number of protons.

• Compounds: Substances of two or more elements in specific ratios, e.g., H₂O and CO₂.

• Chemical Bonds: Formed when atoms share or transfer electrons.

2. Chemical Reactions

• Transform substances by breaking/forming chemical bonds, and rearranging atoms.

• Reactants → Bonds break → Products (new substances).

• Follows the conservation of matter (atoms are neither created nor destroyed).

• Energy changes:

  • Endothermic: Absorbs energy.

  • Exothermic: Releases energy.

3. Properties of Carbon

• Forms covalent bonds with up to 4 atoms, creating diverse molecules.

• Main biomolecules:

  • Lipids: Energy storage, cell structure (e.g., fats).

  • Proteins: Structural components, enzymes (e.g., muscle fibers).

  • Nucleic Acids: Genetic information (DNA, RNA).

  • Carbohydrates: Energy sources (e.g., glucose, starch).

4. Carbohydrate Structure and Function

• Composed of C, H, and O.

• Types:

  • Monosaccharides: Single sugar units (e.g., glucose).

  • Polysaccharides: Chains of sugars (e.g., starch).

• Energy: Broken down for cellular processes.

5. Chemical Energy and ATP

• ATP (Adenosine Triphosphate): Main energy currency for cells.

• Structure: Adenine + Ribose + 3 Phosphate groups.

• Energy stored in phosphate bonds is released when ATP → ADP.

6. Matter and Energy in Photosynthesis

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

  • Inputs: Carbon dioxide, water, light.

  • Outputs: Glucose, oxygen.

• Occurs in chloroplasts:

  • Light-dependent reactions: Capture energy in thylakoid membranes.

  • Light-independent reactions (Calvin Cycle): Form glucose in the stroma.

7. Transforming Light Energy

• Electron Transport Chain: Converts light into chemical energy (ATP, NADPH).

• Stages:

  • Light excites electrons in Photosystem II → Photosystem I.

  • Energy from electron flow creates ATP and NADPH.

Questions and Answers

1. What is the smallest unit of matter?

   • Answer: An atom.

2. What are the reactants and products in photosynthesis?

   • Answer:

     • Reactants: CO₂, H₂O, and light.

     • Products: C₆H₁₂O₆ (glucose) and O₂ (oxygen).

3. How does ATP store and release energy?

   • Answer: Stores energy in high-energy phosphate bonds; releases energy when a bond is broken (ATP → ADP).

4. Name two types of chlorophyll and their role in photosynthesis.

   • Answer:

     • Chlorophyll a and Chlorophyll b absorb light energy, initiating photosynthesis.

5. What are the four main groups of carbon-based compounds in living organisms?

   • Answer: Lipids, proteins, nucleic acids, and carbohydrates.

The light-dependent reactions of photosynthesis occur in the thylakoid membranes of the chloroplasts. During this phase, light energy is captured primarily by chlorophyll a and chlorophyll b pigments. Chlorophyll a is the main pigment responsible for absorbing light in the red spectrum, while chlorophyll b assists by absorbing light in the blue and orange wavelengths. This ensures a more efficient capture of sunlight for the photosynthetic process.

As photons from sunlight strike the chlorophyll molecules, energy is transferred to electrons, exciting them to a higher energy level. These high-energy electrons are then passed through a series of proteins in the electron transport chain. This process generates ATP through photophosphorylation and NADPH as the electrons are ultimately transferred to NADP+.

Additionally, the light energy is utilized to split water molecules (a process known as photolysis) into oxygen, protons, and electrons. This splitting of water not only releases oxygen as a byproduct, contributing to the atmospheric oxygen we breathe but also provides the necessary electrons to replace those lost by chlorophyll during the excitation process.

The ATP and NADPH generated in the light-dependent reactions are then utilized in the light-independent reactions, commonly referred to as the Calvin Cycle, which takes place in the stroma of the chloroplast. The Calvin Cycle uses ATP and NADPH to fix carbon dioxide and synthesize glucose, allowing plants to store energy in a usable form. Thus, the light-dependent reactions are essential for providing the energy carriers needed for the subsequent reactions that contribute to the plant's growth and energy storage.