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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Abiotic and Biotic Factors
Ecosystems are incredibly complex and fascinating systems where living organisms interact with each other and their physical environment. To understand how ecosystems work, we need to look at two main types of factors: abiotic and biotic.
Key Definitions:
These are the non-living parts of an ecosystem that affect the distribution and behaviour of organisms:
These are the living parts of an ecosystem that interact with each other:
Abiotic factors play a crucial role in determining which organisms can survive in a particular habitat. Let's explore some key abiotic factors and their effects:
Affects enzyme activity, metabolic rates and reproduction. Each species has an optimal temperature range.
Example: Polar bears have thick fur and a layer of blubber to survive in cold Arctic temperatures.
Essential for photosynthesis in plants. Affects growth patterns, flowering and animal behaviour.
Example: Plants in forest understory have larger leaves to capture limited light.
Crucial for all life processes. Availability affects species distribution and adaptations.
Example: Cacti store water and have reduced leaves (spines) to minimise water loss.
Affects plant growth, seed dispersal and can cause physical stress.
Example: Trees in windy areas often have stronger, more flexible trunks.
Affects nutrient availability and can directly impact organism survival.
Example: Heather thrives in acidic soils where other plants cannot grow.
Mineral content, texture and structure affect plant growth and soil organisms.
Example: Clay soils retain water better than sandy soils.
Biotic factors involve all the ways living organisms interact with each other. These interactions shape ecosystems and influence population sizes.
Predators hunt and eat other animals (prey). This relationship controls population sizes and can drive evolution.
Example: Lynx and snowshoe hare populations in Canada show cyclical patterns – when hare numbers increase, lynx numbers follow, leading to more predation and eventual decline in hares.
Organisms compete for limited resources like food, water, space, or light. Competition can be:
Example: Different bird species competing for the same nesting sites or food sources.
Close interactions between different species:
Organisms that break down dead material and recycle nutrients back into the ecosystem.
Example: Fungi and bacteria decompose leaf litter in forests, returning nutrients to the soil for plants to use.
Over time, organisms develop adaptations to help them survive in their specific environments. These adaptations can be structural, behavioural, or physiological.
Physical features that help organisms survive.
Examples:
Actions that help organisms survive.
Examples:
Internal processes that help organisms survive.
Examples:
The Sahara Desert is one of the harshest environments on Earth, with extreme abiotic conditions:
Despite these challenges, organisms have adapted remarkably:
This ecosystem demonstrates how abiotic factors shape the adaptations of organisms and how biotic interactions (like food webs) must function within these environmental constraints.
Scientists use various tools to measure abiotic factors in ecosystems:
These measurements help scientists understand how abiotic factors influence the distribution and abundance of organisms in different habitats.
Human activities can significantly alter both abiotic and biotic factors in ecosystems:
Understanding the delicate balance of abiotic and biotic factors helps us predict how ecosystems might respond to these changes and develop conservation strategies.
Abiotic and biotic factors don't exist in isolation – they form a complex web of interactions:
By studying these interactions, ecologists can better understand how ecosystems function and how they might respond to environmental changes in the future.
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