Natural Selection (IB Topic D4.1)

Essential Idea(s): Life evolves. Variations in genes result in variations in traits. Some of those traits end up giving certain organisms an advantage at survival. Environments change, too – so the ability to adapt and evolve is essential for life on earth.

Unit Length: 3 Lessons

*AHL Natural Selection is the unit titled “Gene Pools (D4.1)”

Guiding Questions

◊ What processes can cause changes in allele frequencies within a population?

◊ What is the role of reproduction in the process of natural selection?

Materials:

Self-Teaching Slides (SL)	Quizlet Vocab Set
	Notes Template (SL)

IB Statement(s) and Objective(s)
D4.1.1: Natural selection as the mechanism driving evolutionary change Define natural selection Outline Lamarckism as a mechanism to explain evolution Contrast Darwinism (natural selection) with Lamarckism Explain the concept of natural selection as a mechanism for evolutionary change NOS: Outline the theory of evolution by natural selection as an example of the correspondence, coherence and pragmatic theories of truth D4.1.2: Roles of mutation and sexual reproduction in generating the variation on which natural selection acts Explain why natural selection can only function if there is variation in a species Outline genetic mutations as a source of genetic variation Outline meiosis as a source of genetic variation Outline sexual reproduction as a source of genetic variation Outline gene flow as a source of genetic variation D4.1.3: Overproduction of offspring and competition for resources as factors that promote natural selection Use an example to illustrate the potential for overproduction of offspring in a population State two evolutionary benefits of overproduction of offspring Describe competition for resources as a consequence of overproduction of offspring Explain the Darwinian concept of “survival of the fittest” List examples of resources that may limit population size D4.1.4: Abiotic factors as selection pressures Define selective pressure Compare density-dependent to density-independent selection pressures State that abiotic selection pressures are typically density independent D4.1.5: Differences between individuals in adaptation, survival and reproduction as the basis for natural selection Define adaptation and fitness Explain the effect of the selective pressure on the more and less adapted individuals in a population Explain adaptation as a consequence of natural selection D4.1.6: Requirement that traits are heritable for evolutionary change to occur Distinguish between heritable and acquired characteristics Explain why only heritable characteristics can be acted upon by natural selection D4.1.7: Sexual selection as a selection pressure in animal species Define sexual selection Describe examples of sexual selection, including for color, size, and courtship behaviors D4.1.8: Modelling of sexual and natural selection based on experimental control of selection pressures NOS Concept: Explain what models are and their purposes in science Summarize John Endler’s experiments with guppies which demonstrate selection for and against coloration in different habitats

IB Statement(s) and Objective(s)

D4.1.1: Natural selection as the mechanism driving evolutionary change

Define natural selection
Outline Lamarckism as a mechanism to explain evolution
Contrast Darwinism (natural selection) with Lamarckism
Explain the concept of natural selection as a mechanism for evolutionary change
NOS: Outline the theory of evolution by natural selection as an example of the correspondence, coherence and pragmatic theories of truth

D4.1.2: Roles of mutation and sexual reproduction in generating the variation on which natural selection acts

Explain why natural selection can only function if there is variation in a species
Outline genetic mutations as a source of genetic variation
Outline meiosis as a source of genetic variation
Outline sexual reproduction as a source of genetic variation
Outline gene flow as a source of genetic variation

D4.1.3: Overproduction of offspring and competition for resources as factors that promote natural selection

Use an example to illustrate the potential for overproduction of offspring in a population
State two evolutionary benefits of overproduction of offspring
Describe competition for resources as a consequence of overproduction of offspring
Explain the Darwinian concept of “survival of the fittest”
List examples of resources that may limit population size

D4.1.4: Abiotic factors as selection pressures

Define selective pressure
Compare density-dependent to density-independent selection pressures
State that abiotic selection pressures are typically density independent

D4.1.5: Differences between individuals in adaptation, survival and reproduction as the basis for natural selection

Define adaptation and fitness
Explain the effect of the selective pressure on the more and less adapted individuals in a population
Explain adaptation as a consequence of natural selection

D4.1.6: Requirement that traits are heritable for evolutionary change to occur

Distinguish between heritable and acquired characteristics
Explain why only heritable characteristics can be acted upon by natural selection

D4.1.7: Sexual selection as a selection pressure in animal species

Define sexual selection
Describe examples of sexual selection, including for color, size, and courtship behaviors

D4.1.8: Modelling of sexual and natural selection based on experimental control of selection pressures

NOS Concept: Explain what models are and their purposes in science
Summarize John Endler’s experiments with guppies which demonstrate selection for and against coloration in different habitats


Activities: ⓟ = podcast / ⍰ = inquiry 5 / ⓦ = Write it / Ӕ = The academy / Ⓡ = Read it
ⓟ/ⓦ: Fox Farm – The Experiment to Turn Wild Foxes into Domesticated Pets (👫 max 3) Starting in the 1960s, Russian geneticist Dmitry Belyaev started an experiment to see how many generations it would take to turn wild foxes into loveable, cuddly domesticated pets – just like dogs. It happened surprisingly quickly. Watch this video to learn about the experiment, and discuss: 1) How and why natural selection created the fearful and aggressive foxes found in the wild; and 2) how the process of artificial selection worked in Belyaev’s fox population. Make sure you mention genes, and the potential to select for both tame and aggressive foxes. ⓟ/ⓦ: Far from Perfect – When Evolution Isn’t So Impressive (👫 max 3) Biology teachers and hippies alike both love to talk about the perfection of the human body. In reality, nature can be pretty sloppy. Just look at us: humans breathe and eat with the same tube – which enables choking. Until recently, humans died during childbirth more often (and experienced more pain) than almost any other animal – a result of narrowed hips from evolving to walk on two legs. Human knees, for whatever reason, only move in 2 directions, making knee injuries all too common and painful. Read the article, and highlight some of evolution’s greatest foul-ups in humans. In doing so, explain how evolution does not “give organisms what they need,” but instead is a random and selective process. Ⓛ (Simulation): Hawks vs. Mice (👫 max 2) Play with this simulation so that you feel confident in how it works. Record a screencast of the simulation in action, explaining the key steps of Natural Selection as you go (cover all of the ICE AGE components). Make sure you also explore the alleles of the mice populations — show how one allele becomes the most frequent, depending on the beach vs. field environment. Ⓛ (Simulation): What Happens if They All Survive? (👫 max 2) What happens when all the offspring of a species survive, AND there are unlimited resources? Explore the concepts of carrying capacity, exponential growth and logistical growth with this simulation task. Complete the attached worksheet using the website linked within. Ⓛ (Simulation): The Rabbits vs. the Wolves (👫 max 2) Play with this simulation until you are confident with how it works. Then, complete this accompanying worksheet. Make sure you track all the data and thoroughly answer the questions at the end. Ⓛ (Simulation): Modeling Darwin’s Finches (👫 max 2) To begin, print out this sheet (or ask me to) – you will use the (+) and (-) as representations of alleles within a finch population. See how they evolve when you simulate a change in the environment. Follow the instructions to complete the lab and answer all accompanying questions. ⓟ (or role play): Misconception City (👫 max 3) “Evolution is just a theory.” “We evolved from apes.” “Evolution can’t explain complex organs”. “Evolution can’t be proven.” There are dozens of misconceptions about evolution, especially among groups of people that have been actively taught against it. Together with a partner, make a podcast/vlog to debunk the top misconceptions about evolution provided in the link. Choose enough to explain all of the elements of ICE AGE. ⓟ/ⓦ: The Antibiotic Apocalypse (👫 max 2) The discovery of antibiotics saved hundreds of millions of lives in the 20th century. Unfortunately, their widespread use is also the root of their newfound strength – more and more bacteria are evolving into “superbugs” that are resistant to all of our antibiotic treatments. It will only get worse with time. Watch this quality Kurzgesagt video on antibiotics, then use VISTA to explain how superbugs evolved alongside our overuse of antibiotics, and what can be done about this dark side of evolution. 📄: Out of the Ashes: The Dawn of Mammals (💁) The violent meteor impact 65 million years ago was a bad thing for dinosaurs – it marked the end of their very long dominance of Earth. It was – fortunately for us – a very good thing for the future of mammals. Watch this 15-minute video to find out how mammals became the dominant creatures following the impact, and complete this accompanying worksheet. Ӕ: The Academy – Natural Selection (💁) Although students feel like they understand natural selection quite easily, they often find it quite difficult to explain clearly when speaking or writing. Create a Khan-academy style video to help address this (go here for inspiration). Explain natural selection and the steps summarized in ICE AGE, using examples of specific species.