IB MYP 4-5 Biology-Competition- Study Notes - New Syllabus
IB MYP 4-5 Biology-Competition- Study Notes – New syllabus
IB MYP 4-5 Biology-Competition- Study Notes – IB MYP 4-5 Biology – per latest IB MYP Biology Syllabus.
Key Concepts:
- Intraspecific vs interspecific competition
- Resource partitioning and niche differentiation
- Competitive exclusion principle
- Adaptations to reduce competition
Intraspecific vs Interspecific Competition
In nature, organisms often compete for limited resources like food, space, water, or mates. This struggle is called competition, and it can happen within the same species or between different species. Understanding the difference between these two types helps explain changes in population size, distribution, and survival in ecosystems.
Intraspecific Competition
This is competition between individuals of the same species. They need the exact same resources, so competition is often intense.
- Occurs among members of a single species (e.g., two lions fighting for territory).
- Resources competed for: mates, nesting sites, sunlight (in plants), food.
- Strong impact on population size and natural selection (survival of the fittest).
Interspecific Competition
This is competition between individuals of different species that live in the same habitat and rely on similar resources.
- Occurs between two or more species (e.g., wolves vs bears for food).
- Can lead to competitive exclusion (one species outcompetes the other).
- May cause one species to migrate, adapt, or decline in population.
Comparison Table
| Feature | Intraspecific Competition | Interspecific Competition |
|---|---|---|
| Species Involved | Same species | Different species |
| Resources Fought Over | Identical (e.g., mates, territory) | Similar (e.g., food, habitat) |
| Result of Competition | Natural selection, population control | Competitive exclusion, biodiversity impact |
Ecological Importance
- Helps regulate population sizes
- Drives adaptation and natural selection
- Maintains balance in ecosystems
Leads to niche specialization (organisms evolve to reduce competition)
Summary
Competition is a natural part of ecosystems. Whether it’s between lions and hyenas, or two pine trees growing side-by-side, the struggle shapes survival, adaptation, and biodiversity. Understanding intraspecific vs interspecific competition helps explain why species behave the way they do in the wild.
Resource Partitioning and Niche Differentiation
Why Is This Important?
In ecosystems, many species live close together – but they don’t always compete to the point of extinction. Instead, they find ways to coexist by sharing resources or using them differently.
What Is Resource Partitioning?
| Method | Description | Example |
|---|---|---|
| Different places | Each species uses a different part | Birds feeding at different tree levels |
| Different times | Active at different times | Owls (night) vs hawks (day) |
| Different food types | Feeding on different things | Herbivores eating grass vs shrubs |
What Is Niche Differentiation?
Niche = an organism’s role in its environment – what it eats, where it lives, when it’s active, how it behaves.
Niche differentiation means species change their behavior or lifestyle slightly to reduce niche overlap and competition.
- Often the result of natural selection
- Helps closely related species coexist
Real-Life Examples
- Warbler Birds (MacArthur’s Study): 5 species feed in different parts of the same tree → spatial partitioning
- Desert Rodents: One feeds during the day, one at night → temporal partitioning
- Coral Reef Fish: Hunt at different depths or feed on different prey → niche differentiation
Comparison: Resource Partitioning vs Niche Differentiation
| Feature | Resource Partitioning | Niche Differentiation |
|---|---|---|
| Focus | How species share resources | How species adjust their niche |
| Driven by… | Competition avoidance | Natural selection over time |
| Outcome | Species use separate resource areas | Niches become more specialized |
| Time scale | Can be short-term or behavioral | Usually, long-term evolutionary |
Why This Helps Biodiversity
- Reduces competition between species
- Allows more species to live together in the same habitat
- Supports ecosystem stability and species richness
In nature, species avoid constant competition by sharing resources or changing their roles.
These strategies – resource partitioning and niche differentiation – help organisms coexist and support biodiversity.
Competitive Exclusion Principle
What Is the Competitive Exclusion Principle?
Eventually, one will:
- Outcompete the other
- The weaker species will be excluded – forced to leave, adapt, or die out
Who Discovered It?
The principle was popularized by G.F. Gause, a Russian scientist who studied microscopic organisms in lab experiments.
Gause’s Experiment
- Grew two Paramecium species: P. aurelia and P. caudatum
- When grown alone: both survived well
- When grown together: P. aurelia always outcompeted P. caudatum
Why Does This Happen?
Because both species:
- Use the same resources (food, space, niche)
- One is more efficient or better adapted
- Over time, the weaker species declines
What Is a Niche?
Niche = an organism’s role in its environment – what it eats, where it lives, when it’s active, etc.
- If two species have identical niches, they will compete
- Nature usually encourages slight differences to avoid extinction
Real-Life Examples
| Example | Competitive Outcome |
|---|---|
| Red vs grey squirrels (UK) | Grey squirrels outcompeted reds in many areas |
| Native bird’s vs invasive bird’s | Invasive species take over nesting spaces |
| Barnacle species on rocky shores | Each dominates a different vertical zone |
What Can Happen Instead of Exclusion?
Species share the same area by using different resources or using them at different times.
Example: Two birds feed on the same tree – one eats bark insects, the other eats from leaves.
Summary Table
| Term | Meaning |
|---|---|
| Competitive exclusion | One species eliminates another from a shared niche |
| Niche | The role an organism plays in its environment |
| Resource partitioning | Sharing resources to reduce direct competition |
| Gause’s experiment | Lab test proving competitive exclusion using Paramecium |
Two species can’t survive long-term if they compete for the exact same resources.
The better competitor survives, the other is excluded – unless it adapts or shifts niche.
This principle explains how biodiversity and species balance emerge in ecosystems.
Adaptations to Reduce Competition
In nature, when many species live in the same habitat, competition for resources like food, water, space, and mates is common. To survive and thrive, organisms develop adaptations that reduce direct competition. These changes help species coexist peacefully by using resources in different ways, at different times, or in different places.
Why Reduce Competition?
- Competition uses up energy and reduces survival chances.
- Avoiding direct conflict allows more species to share the same habitat.
- It increases biodiversity and ecosystem stability.
Types of Adaptations That Reduce Competition
- Structural Adaptations:
- Different beak shapes in birds (e.g., finches) to eat different types of food.
- Roots of desert plants grow deeper or wider to avoid sharing water sources.
- Behavioral Adaptations:
- Nocturnal animals (active at night) avoid competing with daytime species.
- Birds nesting in different trees or at different heights.
- Temporal Adaptations:
- Plants flowering at different times of the year to avoid pollinator competition.
Related Concepts
- Resource Partitioning: When species divide up resources to reduce direct overlap and competition.
- Niche Differentiation: Evolutionary process where species adapt to different roles or conditions.
Summary Table
| Type of Adaptation | How It Reduces Competition | Example |
|---|---|---|
| Structural | Allows use of different physical resources | Beak shapes in finches |
| Behavioral | Avoids competition in time or space | Nocturnal vs diurnal animals |
| Temporal | Reduces overlap in resource use | Plants flowering at different times |
Why It Matters
- Helps multiple species coexist in the same habitat.
- Promotes biodiversity and healthy ecosystems.
- Reduces stress and competition pressure on organisms.
Summary
Adaptations to reduce competition are key to survival in shared ecosystems. By changing their behavior, structure, or timing, organisms avoid constant struggles and find unique ways to live. These adaptations allow nature to support more life, with less conflict.