Life on Earth N5 Biology: Unit 3 Mind Maps Overview

Environmental Factors and Species Distribution

Ever wondered why polar bears live in the Arctic but not in tropical rainforests? It's all about biotic and abiotic factors that determine where organisms can survive.

Biotic factors are the living influences on organisms - think predation, disease, competition for food, and grazing. These biological interactions shape which species can thrive in any given area. Abiotic factors are the non-living environmental conditions like temperature, pH, soil quality, water availability, and light intensity.

Scientists use indicator species to assess environmental quality. These are organisms whose presence or absence tells us about the health of an ecosystem. For example, lichens indicate clean air quality, whilst their absence suggests pollution.

Quick Tip: Remember biotic = biological (living), abiotic = not biological (non-living). Simple!

Researchers measure these factors using various tools like pH meters for acidity, light meters for brightness, and pitfall traps for counting small animals. The key is taking multiple samples and avoiding errors like shadows affecting light readings or forgetting to clean equipment between measurements.

Sustainable Food Production Methods

Modern agriculture faces a massive challenge: feeding billions whilst protecting our planet. Biological control offers a clever solution by using natural predators to control pests, like introducing Argentine moths to tackle invasive Australian cactus.

Genetically modified (GM) crops are engineered to resist pests naturally, reducing the need for harmful pesticides. This makes them more environmentally friendly than conventional crops. Pesticides kill unwanted organisms but cause bioaccumulation - toxic substances building up in food chains, famously affecting birds of prey with DDT poisoning.

Fertilisers contain nitrates that boost crop yields by providing essential nutrients. Plants absorb these nitrates through their roots and convert them into amino acids for protein production. However, leaching occurs when excess fertilisers wash into water systems.

Environmental Alert: Leaching causes algal blooms that block sunlight, killing aquatic plants and creating oxygen-starved dead zones that devastate entire ecosystems.

The two main alternatives to pesticides are biological control and GM crops - both offering sustainable solutions to pest management without environmental damage.

Evolution and Species Formation

Evolution isn't just ancient history - it's happening right now around us! A species is defined as organisms that can interbreed and produce fertile offspring, which explains why horses and donkeys aren't the same species (their offspring, mules, are sterile).

Natural selection drives evolution through a simple process: environmental pressures favour the best-adapted individuals, who survive to reproduce and pass on their advantageous traits. Over time, these favourable alleles become more common in the population.

Speciation occurs when populations become separated by isolation barriers. Geographical barriers like mountains and rivers physically separate groups, whilst behavioural barriers like different courtship rituals prevent mating between populations. Over time, these isolated groups evolve differently and can no longer interbreed.

Mutations - random changes in genetic material - provide the raw material for evolution. Mutagenic agents like radiation and certain chemicals increase mutation rates. Most mutations are harmful or neutral, but occasionally they're advantageous and spread through populations.

Evolution Insight: Variation within species is essential because it allows populations to adapt to changing environmental conditions over time.