Theory of evolution, mendel, and speciation

What is evolution?

• Evolution is the gradual change in species over time.

• It happens because of natural selection.

• Over generations, species develop new traits that help them survive.

natural selection is the process by which ______ happens

evolution

How does natural selection cause evolution?

1⃣ Variation – Organisms in a species have different traits (caused by mutations).
2⃣ Competition – Organisms compete for limited resources (food, mates, shelter).
3⃣ Survival of the fittest – The best-adapted individuals survive/ individuals with advantageous traits
4⃣ Reproduction – Survivors pass their beneficial genes to offspring.
5⃣ Gradual Change – Over time, the species evolves.

what is a species

group of organisms that can interbreed and produce fertile offspring

What evidence do scientists have for evolution?

✅ Fossil record – Shows how species have changed over millions of years.
✅ DNA evidence – Similar DNA between species shows common ancestry.
✅ Comparative anatomy – Similar bone structures in different animals.
✅ Antibiotic resistance – Bacteria evolve to survive antibiotics.

What did Charles Darwin propose?

Species evolved over time from simple life forms because of variation and survival of the fittest.

Why was Darwin’s theory not widely accepted at first?

❌ It contradicted religious beliefs about creation.
❌ There was not enough evidence at the time (fossils and DNA were not well understood).
❌ Genetics were not yet discovered, so he couldn’t explain how traits were inherited.

What is speciation?

Speciation is the process by which new species form.

What are the steps in speciation?

1⃣ Isolation – A population is separated (e.g., by a river, mountains, or climate change).
2⃣ Different Environments – Each group adapts to its new surroundings.
3⃣ Natural Selection – Different traits become favorable in each group.
4⃣ Genetic Differences – Over time, changes accumulate, and the groups become too different to interbreed.
5⃣ New Species Formed – They can no longer reproduce together.

How do bacteria show rapid evolution?

• Bacteria reproduce very quickly.

• Mutations can make some resistant to antibiotics.

• These bacteria survive and reproduce, leading to antibiotic-resistant strains (e.g., MRSA).

Who was Gregor Mendel, and what did he discover?

• He experimented with pea plants and discovered inheritance patterns.

• He found that characteristics are passed on in predictable ways.

Mendel’s Key Discoveries:
✅ Genes exist in pairs (now called alleles).
✅ Some traits are dominant, others are recessive.
✅ Traits are inherited from parents.

Why was Mendel’s work not understood at the time?

❌ He was a monk, not a famous scientist.
❌ DNA and genes were not discovered yet.
❌ Scientists at the time did not understand statistics in biology.

His ideas were later confirmed when chromosomes and DNA were discovered.