Ecosystem Basics

Think of an ecosystem as nature's neighbourhood - it includes all the living creatures plus non-living things like rocks and water in one area. Your local park is a perfect example!

A habitat is simply where an organism calls home, whilst a population counts how many of the same type of organism live there. All these different populations together form a community - like all the residents in that neighbourhood.

Biodiversity measures how many different species (groups that can breed together and have fertile babies) live in one ecosystem. More variety usually means a healthier ecosystem that can bounce back from problems.

Quick Tip: Remember that ecosystems include both living AND non-living components - don't forget about things like soil and weather!

Food Chains and Webs

Food chains show who eats whom in a simple line: producer → primary consumer → secondary consumer → tertiary consumer. It's like following a meal from grass to rabbit to fox!

Food webs are much more realistic because they show complex feeding relationships where organisms often eat multiple things. Think of it as a tangled web rather than a straight line.

Producers are green plants that make their own food through photosynthesis. Consumers get energy by eating other organisms - herbivores munch plants, carnivores eat meat, and omnivores enjoy both.

Energy flows through these feeding relationships, powering every living thing in the ecosystem.

Remember: Energy always flows in one direction through food chains, but gets passed between many different organisms in food webs!

Ecological Niches and Competition

Your niche is basically your job description in nature - it includes what you eat, where you live, and how you interact with other organisms. Every species has its own unique role to play.

Competition kicks off when two organisms want the same limited resources. Animals typically fight over food, water, and living space, whilst plants compete for light, water, minerals, and root space.

This competition happens because niches overlap - when species need similar things, they end up competing for survival. It's like students competing for the last slice of pizza at lunch!

The organisms that are better at competing survive longer and pass on their genes to the next generation.

Think About It: Competition drives evolution - only the best competitors get to reproduce and pass on their winning traits!

Types of Competition

Interspecific competition happens between different species - like foxes and owls both hunting for the same mice. Intraspecific competition occurs within the same species - like two foxes competing for territory.

Intraspecific competition is usually much fiercer because members of the same species need exactly the same resources. Two red squirrels will fight harder over acorns than a squirrel and a bird would.

The winners of these competitions survive longer, reproduce more, and pass their successful genes to their offspring. This process helps drive natural selection and evolution.

Key Point: Same-species competition is more intense because they have identical needs - it's the survival of the fittest in action!

Environmental Factors and Sampling

Environmental factors split into two camps: abiotic factors $non-living things like pH, temperature, and light intensity$ and biotic factors (living influences like competition, predation, and disease).

Scientists use specific tools to measure these factors: light meters for brightness, moisture meters for soil dampness, pH meters for acidity, and quadrats to count organisms in a specific area.

Pitfall traps help researchers catch small animals living in leaf litter - they're basically harmless containers buried in the ground that creatures accidentally fall into.

Understanding these factors helps scientists figure out why certain organisms thrive in some places but struggle in others.

Pro Tip: Environmental monitoring is crucial for conservation - knowing what affects organisms helps us protect their habitats!

Identification and Water Pollution

Keys are identification tools that help scientists work out what species they've found. Branching keys and paired statement keys both guide you through yes/no questions until you identify your mystery organism.

Indicator species act like nature's pollution detectors - their presence or absence tells us about pollution levels. It's like having biological warning systems built into ecosystems!

Water pollution occurs when harmful substances like untreated sewage contaminate water bodies. Bacteria break down this sewage but use up oxygen in the process, suffocating aquatic life.

Clean water hosts mayfly larvae and freshwater shrimps, whilst polluted water might only support tough species like rat-tailed maggots.

Environmental Alert: The absence of sensitive species often tells us more about pollution than the presence of pollution-tolerant ones!

Air Pollution Indicators

Lichen serves as an excellent indicator species for air quality. These crusty, leafy, or bushy organisms are extremely sensitive to air pollutants, making them perfect biological monitors.

Clean air supports bushy lichens, moderately polluted areas might have leafy lichens, and heavily polluted zones typically only support crusty lichens. Areas with no lichen at all usually have severely polluted air.

Some pollution-tolerant species can survive in both clean and dirty environments. However, it's the absence of sensitive species that really reveals pollution problems.

Nature's Warning: Think of lichen as nature's air quality app - the more variety you see, the cleaner the air!

Photosynthesis: The Light Reaction

Photosynthesis is nature's way of converting sunlight into food: carbon dioxide + water → sugar + oxygen (with light and chlorophyll doing the work). It's literally how plants eat sunshine!

Chloroplasts contain chlorophyll, the green pigment that traps light energy. Photosynthesis happens in two main stages: the light reaction and carbon fixation.

During the light reaction, light energy gets converted into chemical energy (ATP). The absorbed light also splits water molecules into hydrogen and oxygen - that's why we get oxygen as a byproduct.

ATP forms when ADP combines with inorganic phosphate, storing energy for the plant's use. This process is controlled by enzymes and provides the power for the next stage.

Amazing Fact: Every breath of oxygen you take comes from photosynthesis - plants literally give us the air we breathe!

Light Reaction Process

The light reaction follows a straightforward sequence: light energy splits water molecules, releasing oxygen and hydrogen whilst converting ADP into energy-rich ATP.

This reaction captures and converts light energy into chemical energy that plants can actually use. Think of it as nature's solar power system, turning sunlight into batteries (ATP) that store energy.

The hydrogen produced here gets saved for the next stage of photosynthesis, whilst oxygen gets released into the atmosphere as a bonus for all oxygen-breathing organisms.

Energy Conversion: The light reaction is essentially a biological solar panel that powers all plant processes!

Carbon Fixation

Carbon fixation is where the magic happens - ATP, hydrogen, and carbon dioxide combine to create glucose (sugar). It's like nature's kitchen where simple ingredients become food!

Plants can use this newly made sugar immediately for respiration (their version of breathing), store it as starch for later, or convert it into cellulose to build strong cell walls.

This stage doesn't directly need light, which is why it's sometimes called the dark reaction. However, it absolutely depends on the ATP and hydrogen produced during the light reaction.

The glucose created here becomes the foundation of virtually all food chains on Earth - making photosynthesis the process that feeds our entire planet.

Global Impact: Carbon fixation doesn't just feed plants - it creates the energy source for almost every living thing on Earth!