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# Quick check: evidence, new species and evolution today

Year 10 Biology · Evolution

<!-- Speaker note: A self-test on the lines of evidence for evolution, speciation and extinction, and evolution in present populations (AC9S10U02, nodes 3, 4 and 5, taught in class; node 3 a hinge). About 16 minutes (Node 3 5 min · Node 4 5 min · Node 5 6 min). -->

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## Today

**We are learning to** a few quick questions on the evidence for evolution, how new species form and die out, and evolution happening now. Taught in class; use this to check yourself.

- I can give three kinds of evidence for evolution.
- I can explain how a new species can form and why one goes extinct.
- I can use natural selection to explain antibiotic resistance.

<!-- Speaker note: Before class: A Quick check: a few questions on what students should know for AC9S10U02 nodes 3, 4 and 5, which you teach in class. It has no board, no clip and no new teaching, and it is optional, so it never holds up course completion. Set the width with `?width=minimum`, `typical` (default) or `wider`. Use it as a self-test after your teaching, a starter, or revision. Variation and natural selection are on screen (nodes 1 and 2). Evidence and the extended examples are for class; fossils, models and case studies work best in hand. Check your school's approach to teaching evolution and present it as the scientific theory with its evidence. Teacher: Node 3: ask for a third line of evidence out loud after the sort. Teacher: Node 5: ask students to retell the resistance story in their own words. -->

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## Why it matters

> Whales have finger bones. Bacteria shrug off drugs. What do they have in common?

<!-- Speaker note: Your teacher covers the evidence and the examples in class. These questions check the basics of how natural selection explains the past and the present. -->

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## Evidence or not?

**Is it evidence for evolution?**

Groups: Evidence · Not evidence

Fossils in layers, with simpler forms in older rock · Similar bones in a human arm, a bat wing and a whale flipper · DNA more similar between closely related species · Related animals living in the same region, such as Australian marsupials · Two animals that are the same colour

* Answer: Fossils in layers, with simpler forms in older rock → Evidence; Similar bones in a human arm, a bat wing and a whale flipper → Evidence; DNA more similar between closely related species → Evidence; Related animals living in the same region, such as Australian marsupials → Evidence; Two animals that are the same colour → Not evidence

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## Why several?

**Why do scientists place so much weight on several lines of evidence?**

- Independent kinds of evidence all point to the same conclusion, which makes it much more reliable
- Each is a different theory
- More evidence is always better, whatever it shows
- One line is enough

* Answer: Independent kinds of evidence all point to the same conclusion, which makes it much more reliable

<!-- Speaker note: Fossils, anatomy, DNA and distribution come from different methods, so agreement is strong support. -->

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## What each shows

**Match each line of evidence to what it shows.**

| | |
|---|---|
| `Fossils in rock layers` | A. Those animals share a common ancestor |
| `Similar bones in an arm, a wing and a flipper` | B. Living things have changed over time, in order |
| `How similar species' DNA is` | C. Species evolved where their ancestors lived, cut off from elsewhere |
| `Marsupials found mostly in Australia` | D. How closely related they are |

* Answer: Fossils in rock layers → B. Living things have changed over time, in order; Similar bones in an arm, a wing and a flipper → A. Those animals share a common ancestor; How similar species' DNA is → D. How closely related they are; Marsupials found mostly in Australia → C. Species evolved where their ancestors lived, cut off from elsewhere

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## New species

**A population is split by a new mountain range. Over a long time the two groups face different conditions. What might happen?**

- Natural selection acts differently on each, and they may become separate species
- Each group changes because its members try to suit their new home
- Nothing changes
- The groups merge

* Answer: Natural selection acts differently on each, and they may become separate species

<!-- Speaker note: Isolated groups cannot share genes, and different pressures favour different traits, so they can diverge until they no longer interbreed. -->

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## Extinction

**Why do species go extinct?**

- They never go extinct naturally
- They choose to stop reproducing
- They are always the weakest species
- The environment changes faster than the population can adapt, or it has no helpful variation

* Answer: The environment changes faster than the population can adapt, or it has no helpful variation

<!-- Speaker note: Selection can only act on variation that already exists. If no individuals can survive the change, the species dies out. -->

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## Fossil timeline

**What does the fossil record show about species over time?**

- Fossils show only species that are now extinct
- All the species alive today are found in the oldest layers
- Species appear and disappear at different times in the rock layers
- The deeper the layer, the bigger the animals

* Answer: Species appear and disappear at different times in the rock layers

<!-- Speaker note: Layers show the order in which groups appear and vanish, which fits change over time. -->

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## Resistant bacteria

**Antibiotics kill most bacteria in an infection, but a few resist. What happens next?**

- Nothing: resistance cannot spread
- The bacteria decide to resist
- The resistant bacteria survive and reproduce, so the population becomes more resistant
- The antibiotic makes the bacteria resistant

* Answer: The resistant bacteria survive and reproduce, so the population becomes more resistant

<!-- Speaker note: The antibiotic is the selection pressure. Resistant bacteria already existed by chance, and the treatment leaves them to multiply. -->

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## Pesticide

**A farmer sprays the same pesticide for years and it works less well. Why?**

- The insects moved away
- The insects learned to ignore it
- The pesticide wore out
- Insects that happened to resist survived and bred, so resistance became common

* Answer: Insects that happened to resist survived and bred, so resistance became common

<!-- Speaker note: Selection pressure over many generations raises the share of resistant individuals. -->

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## Individuals or populations?

**Which statement about evolution is correct?**

- Evolution only happened in the past
- Populations change over generations; individuals do not evolve in their lifetime
- Evolution has a goal
- Individuals change to suit their surroundings

* Answer: Populations change over generations; individuals do not evolve in their lifetime

<!-- Speaker note: Individuals do not change their genes to fit; the proportions of traits in the population change as some survive and reproduce more. -->

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## Why so many species?

**Why are there millions of different species today?**

- All of today's species have existed unchanged since life began
- New species stopped forming once humans appeared
- Every species has been evolving towards being human
- Over billions of years, natural selection in different environments has split populations into many species, and it still goes on

* Answer: Over billions of years, natural selection in different environments has split populations into many species, and it still goes on

<!-- Speaker note: Today's biodiversity is the result of the same processes still at work: variation, selection and isolation. -->

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## Exit ticket

**Explain in two sentences how bacteria become resistant to an antibiotic.**

* Some bacteria already have resistance by chance. The antibiotic kills the others, so the resistant ones reproduce and become common.

<!-- Speaker note: Students answer on paper or a mini whiteboard before the reveal. Anyone who cannot answer needs the main idea again next lesson. Where this leads: Back in class: a selection simulation; a case study on antibiotic resistance and why courses should be completed. -->