Ecology: Food Chains and Food Webs

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### Food Chains and Food Webs
- A food chain illustrates a linear sequence of organisms where each consumes the one before it, transferring energy and nutrients.
- A food web is a complex network of interconnected food chains, showing the diverse feeding relationships within an ecosystem.
- Producers (e.g., plants) form the base of a food chain, converting sunlight into energy through photosynthesis.
- Consumers obtain energy by feeding on other organisms; they can be herbivores, carnivores, or omnivores.
- Decomposers (e.g., bacteria and fungi) break down dead organisms, returning nutrients to the ecosystem.
- Energy transfer in a food web is inefficient; only about 10% of the energy at one trophic level is transferred to the next, the rest is lost as heat.
- Disruptions to a food web, such as the removal of a keystone species or the introduction of an invasive species, can have cascading effects on the ecosystem.
- Bioaccumulation refers to the increasing concentration of toxins in organisms at higher trophic levels.

### Harm to Ecosystems
- Pollution, including chemical runoff and plastic waste, degrades habitats and harms wildlife.
- Deforestation reduces biodiversity, disrupts water cycles, and contributes to climate change.
- Overfishing depletes fish populations and disrupts marine ecosystems.
- Climate change leads to habitat loss, altered migration patterns, and increased frequency of extreme weather events.
- Invasive species can outcompete native species, alter food webs, and transmit diseases.

### Force, Weight, and Mass
- Force is a push or pull that can change the motion of an object; measured in newtons (N).
- Weight is the force of gravity acting on an object's mass; also measured in newtons (N).
- Mass is the amount of matter in an object; measured in kilograms (kg).
- Weight = mass × gravitational acceleration (approximately 9.8 m/s² on Earth).
- An object's mass remains constant, but its weight can change depending on the gravitational field.

### Floating and Sinking
- An object floats if the buoyant force (upward force exerted by a fluid) is equal to or greater than its weight.
- An object sinks if its weight is greater than the buoyant force.
- Density is mass per unit volume (ρ = m/V); an object floats if its density is less than the density of the fluid.
- Archimedes' principle: the buoyant force on an object is equal to the weight of the fluid it displaces.

### Electrical Circuits and Components
- An electrical circuit is a closed loop that allows electric current to flow.
- Key components include:
  -  Power source (e.g., battery) provides voltage.
  -  Wires conduct current.
  -  Resistors limit current flow.
  -  Switches control the flow of current.
  -  Light bulbs convert electrical energy into light and heat.
- Current (I) is the rate of flow of electric charge; measured in amperes (A).
- Voltage (V) is the electrical potential difference; measured in volts (V).
- Resistance (R) is the opposition to current flow; measured in ohms (Ω).
- Ohm's Law: V = IR (Voltage = Current × Resistance).
- Series circuits: components are connected in a single path; current is the same through each component, and voltages add up.
- Parallel circuits: components are connected in multiple paths; voltage is the same across each component, and currents add up.

Explore food chains as linear sequences of energy transfer and food webs as interconnected networks. Understand the roles of producers, consumers, and decomposers within ecosystems. Learn about energy transfer efficiency and the impacts of disruptions on ecological balance.