Ch.22

Front 1

Artificial Selection (def)

Back 1

: The selectivebreeding of domesticated plants and animals to encourage the occurrence ofdesirable traits;

Front 2

Descent with modification (def)

Back 2

Darwin’s initial phrase for the general process of evolution.

Front 3

Evolutionary Adaptation (Def)

Back 3

An accumulation of inherited characteristics thatenhance organisms’ ability to survive and reproduce in specific environments.

Front 4

Natural Selection (Def)

Back 4

Differential success in the reproduction of differentphenotypes resulting from the interaction of organisms with their environment.

Front 5

3 major observations of life are:

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1.Life forms share many common traits (unity)

2.Life forms have many differences as well (diversity)

3.Life forms are matched to their environments

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The Theory of Evolution strives to provide a:

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biological mechanism to explain these 3 observations

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Charles Darwin was a -

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British naturalist who presented what we now call evolutionary theory(he referred to it as “Descent with Modification”) in his groundbreaking book“The Origin of Species”

Front 8

The main idea behind Darwin’s theory is that:

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organisms can vary in their inherited traits and notall variations are as likely as others to foster survival and thereforereproductive success

Front 9

Those organisms that possess traits better adapted tothe current environment will survive over:

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those that do not have those traits and will thereforepass the inherited traits on to their offspring

Front 10

This preferential survival of some traits over othersis called

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Natural Selection

Front 11

Artificial selection occurs when:

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humans selectively breed certain desirable traits withsometimes little regard to natural survival possibilities '

Front 12

Aristotle:

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Believed in a scalanaturae or a fixed ladder of life on which organisms

Front 13

Key points about evolution and natural selection

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--- Only inherited traits are those that natural selection can work on

---These traits must be found in variations in the population

---Natural selection for some traits over others will change if theenvironmental pressures change

Front 14

Whatwere some of the major observations Darwin made on his voyage on the HMSBeagle?

Back 14

Darwin noticed species that were closer geographically weremore similar to each other than comparing species from different areas, such asthe tropics versus temperate areas. His witnessing of an earthquake in SouthAmerica and the subsequent change in the geology of the land made himquestion again the age of the Earth and how change over time in the Earth’s surfacecould explain the movement of fossils from earlier times. The GalapagosIslands off the coast of South America forced him to further think about thegeographic distribution of species as he noticed different species of birds and otheranimals between the different islands and he began to notice the specificadaptations different species had in their unique environments. These observations madehim think more about how species might develop after they had beenseparated from the mainland and were able to speciate each island in possiblydifferent ways.

Front 15

Explainhow adaptations and natural selection work together as the driving forcesbehind evolution.

Back 15

Adaptations are inherited characteristics of organisms thatenhance their survival and reproduction in specific environments. Natural selectionis a process in which individuals that have certain inherited traits tend tosurvive and reproduce at higher rates than other individuals because of thosetraits. In a nutshell, the organisms that are best adapted to their particularenvironment will be the ones natural selection will “allow” to live better and reproducemore so therefore the specific genes that are responsible for the best suitedadaptations will be the ones most likely passed on and be in the next generation.Over time, this leads to possible changes in the populations as those with thebest traits for survival are more represented in the population. If the environmentchanges, even very slowly, over time natural selection will alter whichadaptations are the best suited and this can lead to changes in species, even to the pointof a new species emerging.

Front 16

How does variation in a population and differential survivalrate contribute to evolution?

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Darwin realized that in order for natural selection to takeplace, organisms needed to be genetically different from each other or at thevery least, there needed to be the potential for genetic variation. We knownow much of that variation comes from possibility of mixing DNA during eventssuch as crossing over during meiosis or random mutations but in the end,whatever the cause of the variation, there are genetic differences betweenorganisms in populations. Species are not just clones of each other with identicalDNA. Once there is genetic difference, that may cause some organisms to survivebetter than others and therefore their genomes passed on more frequently tomore offspring. The second part, the differential survival rate, is importantbecause it sets up the pressure for some organisms to survive and others not tosurvive. Organisms generally produce more offspring than can possibly survivebased on the available resources such as food or shelter. That forcesthose that have a better chance at surviving—whether having better skills at findingthe limited resources or somehow ensuring that their offspring survive whileothers don’t, will be selected for. If there was always plenty of resources, allorganisms, regardless of their adaptations would pass on their genes and thereforenatural selection would not have a driving force.

Front 17

Discusshow antibiotic resistant bacterial species is evidence of evolution.

Back 17

A common misconception about evolution is that you can notstudy the process over a shorter time frame so you need to depend on fossilevidence and other data that is not as direct as watching evolution happen morequickly. However when you study species such as bacteria that can reproducevery quickly and therefore go through many more generations in a relativelyshort period of time, scientists can witness evolution “first hand” so to speak.In the case of antibiotic resistance in bacteria such as MRSA, what we are seeing isthe ability of some bacteria to have a natural resistance to the antibioticsthat would normally kill them. Let’s say for the sake of argument, the originalpopulation of bacteria has 1 million cells and 999,999 of them died with exposed to anantibiotic. But just one of those bacterial cells had a random mutation that made itnot be effected by the antibiotic for some reason so it lived. It will thereforepass on its genes to its offspring and they would also survive if they also have this“resistance gene”. Even if other populations of bacteria nearby did not havethe gene to protect them and therefore also died with exposure, over time (andwith bacteria, that time scale is rapidly sped up since they can reproduce soquickly and in vast quantities), many of the bacterial cells in the populationcould end up having the resistance to the antibiotic.