Many students feel confused when they see the long phrase “environmental factors can influence natural selection because they can increase or decrease…”
The confusion usually happens around the words increase and decrease — what they mean, when to use them, and how they change the meaning of a sentence.
This guide will make everything simple.
You will learn the meaning, difference, and correct usage of increase and decrease when they appear in scientific sentences like the focus keyword: environmental factors can influence natural selection because they can increase or decrease something in the environment.
By the end, even a 4th-grade student will understand these words clearly.
We’ll use plain English, clear examples, a comparison table, a recap section, a mini-quiz, and easy memory tricks.
Let’s begin!
What Does Each Word Mean?
To understand the focus keyword environmental factors can influence natural selection because they can increase or decrease, you first need to understand what increase and decrease actually mean.
Meaning of “Increase”
Increase means to go up, grow, or become more.
It is usually a verb, but it can also be a noun.
Simple examples of “increase”
- The price of apples can increase when fewer apples grow.
- My reading speed increased after I practiced every day.
- A warm climate can increase the number of insects.
Mini-Story:
Imagine you have 5 candies. Your friend gives you 5 more.
Your candies increase from 5 to 10.
Meaning of “Decrease”
Decrease means to go down, shrink, or become less.
It is also usually a verb, but it can be a noun too.
Simple examples of “decrease”
- The number of birds may decrease in winter.
- If you study less, your grades may decrease.
- A shortage of food can decrease a population.
Mini-Story:
Imagine you have 10 candies but you eat 6.
Your candies decrease from 10 to 4.
The Key Difference Between Increase and Decrease
Here is the simple difference:
- Increase = go up
- Decrease = go down
This difference helps explain why environmental factors can influence natural selection because they can increase or decrease important things like food, temperature, predators, or population sizes.
Comparison Table: Increase vs Decrease
| Feature | Increase | Decrease |
|---|---|---|
| Meaning | To go up | To go down |
| Opposite Word | Decrease | Increase |
| Used When | Something becomes more | Something becomes less |
| Example Sentence | “Rainfall can increase plant growth.” | “Lack of rain can decrease plant growth.” |
Quick Tip to Remember
Think of a thermometer:
- When the red line goes up, things increase.
- When the red line goes down, things decrease.
Common Mistakes and How to Avoid Them
Even older students mix them up. Here are the most common mistakes.
❌ Mistake 1
“Food shortage can increase the population.”
✅ Corrected Version
“Food shortage can decrease the population.”
Why?
Shortage means less food, so population should go down, not up.
❌ Mistake 2
“Warm temperatures can decrease insect activity.”
✅ Corrected Version
“Warm temperatures can increase insect activity.”
Why?
Most insects are more active when it’s warm.
❌ Mistake 3
“Natural selection works only when things decrease.”
✅ Corrected Version
“Natural selection works when things increase or decrease.”
Why?
Natural selection depends on any change — up or down.
When to Use “Increase”
You use increase when something becomes more, bigger, or higher.
This helps explain why environmental factors can influence natural selection because they can increase or decrease things in nature.
Use “Increase” When:
- Population becomes bigger
- Food supply becomes more
- Temperature gets higher
- Resources grow
- Predators become more common
Examples
- Rain can increase the number of plants.
- More sunlight can increase energy in an ecosystem.
- Good soil can increase crop growth.
- Extra shelter can increase animal survival.
- Warm weather can increase insect reproduction.
When to Use “Decrease”
You use decrease when something becomes less, smaller, or lower.
Use “Decrease” When:
- Food becomes less
- Water becomes less available
- Temperature gets lower
- Predators decline
- Disease causes numbers to go down
Examples
- Drought can decrease plant growth.
- Pollution can decrease fish populations.
- Cold winters can decrease insect activity.
- Low food can decrease bird survival.
- Overhunting can decrease predator numbers.
Memory Hack
Think of the word de in decrease.
De often means down (like descend, decline, deflate).
So:
Decrease = down
Quick Recap: Increase vs Decrease
- Increase = more
- Decrease = less
- Both are used to explain how environmental factors can influence natural selection because they can increase or decrease important conditions in nature.
- Use increase when numbers go up.
- Use decrease when numbers go down.
- If something grows, expands, rises → increase
- If something falls, drops, shrinks → decrease
Advanced Tips
Even though these words are simple, here are a few deeper tips for advanced readers.
1. Origin / History
- Increase comes from Latin increscere, meaning “to grow.”
- Decrease comes from Latin decrescere, meaning “to grow less.”
2. Academic / Essay Use
In essays or science reports, these words show change:
- “Temperature increased by 10°C.”
- “Population decreased after the food shortage.”
3. How Misuse Changes Meaning
Using the wrong one can change the whole idea:
“Predators increased” vs “Predators decreased” —
opposite meanings and opposite effects on natural selection.
Mini Quiz (Test Yourself!)
Fill in the blanks with increase or decrease:
- Heavy rain can ________ the water level in rivers.
- Lack of food can ________ the size of animal groups.
- Warm weather usually ________ insect activity.
- Pollution can ________ fish numbers.
- More sunlight can ________ plant growth.
- Fewer predators can ________ prey population.
- Extreme cold can ________ reptile movement.
(Answers: increase, decrease, increase, decrease, increase, increase, decrease)
FAQs
1. What does “increase” mean in simple English?
It means something goes up or becomes more.
2. What does “decrease” mean in simple English?
It means something goes down or becomes less.
3. Why do we say environmental factors can increase or decrease things?
Because nature always changes. Some factors make numbers go up, and others make them go down.
4. How do these words relate to natural selection?
Natural selection happens when conditions increase or decrease survival, traits, or population sizes.
5. What is the easiest way to remember the difference?
Increase = up
Decrease = down
Conclusion
Now you understand why environmental factors can influence natural selection because they can increase or decrease important parts of the environment.
You also learned the meanings of increase and decrease, how to use them, how to avoid common mistakes, and how they change the meaning of scientific sentences.
Keep practicing these words in daily writing and speaking.
The more you use them, the easier English becomes.
Oliver Thorne is a passionate digital storyteller and content strategist at WordContrast.com. With years of experience in SEO writing and online marketing, he specializes in transforming complex ideas into clear, engaging articles. Oliver loves exploring the latest trends in technology, productivity, and digital culture—helping readers stay informed and inspired in today’s fast-moving world.
