Natural selection

Topic 5.2

Essential idea: The diversity of life has evolved and continues to evolve by natural selection.

Understandings

5.2.U1 Natural selection can only occur if there is variation among members of the same species

Place mouse on figure to view relationship between jellyfish, starfish and human.

Natural selection and variation among species members

5.2.U2 Mutation, meiosis and sexual reproduction cause variation between individuals in a species

Variation caused by meiosis and mutation

5.2.U3 Adaptations are characteristics that make an individual suited to its environment and way of life

Adaptations and the environment

5.2.U4 Species tend to produce more offspring than the environment can support

Place your mouse on figure to view explanation of overpopulation

Overpopulation and the environment

5.2.U5 Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die                      or produce fewer offspring

Pesticide resistance and production of more offspring

5.2.U6 Individuals that reproduce pass on characteristics to their offspring

Pesticide resistance and passing on resistance characteristic

5.2.U7 Natural selection increases the frequency of characteristics that make individuals better adapted and decreases                      the frequency of other characteristics leading to changes within the species

Change in frequency of insecticide-resistant population

Applications

5.2.A1 Changes in beaks on finches on Daphne Major

Where are the Galapagos Islands?

Charles Darwin travelled to the Galapagos Islands aboard the HMS Beagle in 1831. Some of the scientific evidence he gathered during the Beagle expedition was used in his book "The Origin of Species". Specifically, his investigation about the finches of the Galapagos Islands.

Map of the Galapagos Islands

How sexual reproduction promotes variation in a species?

The figure below illustrates that the members of a species (e.g., Galapagos finches) show variation (in beak depth). Explain how sexual reproduction promotes variation in a species.

Place mouse pointer on the figure to view explanation for variation in beak depth.

Beak variation in finches

5.2.A2 Evolution of antibiotic resistance in bacteria

Mechanism of antibiotic resistance

Mechanisms of antibiotic resistance in bacteria
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