7.1 How it all began

• Biologie
• biology
• Middelbare school
• vwo
• Leerjaar 3

Evolution

Some notes on the topic

• I'm not here to tell you what to believe regarding your religion.
• I only expect from you to understand the theory from the perspective of science, not to take it as the truth. 

• Misconceptions

Present day giraffes have long necks because

1. They stretch them to reach the trees for food
2. Their ancestors adapted to have long necks over time
3. Giraffes with the longest necks are the strongest and most perfect
4. Their neck length increases their speed

During the course of evolution, it is often the case that a structure, such as a functional eye, is lost in an animal’s body. This is because ...

1. It is no longer actively used.
2. Mutations accumulate that disrupt its function.
3. It interferes with other traits and functions
4. The cost to maintain it is not justified by the benefits it brings

How can a catastrophic global event influence the course of evolution?

1. Unwanted versions of genes are removed
2. New genes are generated
3. Only some species may survive the event
4. There are short term effects that disappear over time

If you had a bunch of wolves and wanted a Chihuahua, how would you create one?

Darwin's journey

• 1831 - 22 years old
• HMS Beagle
• Collected fossils, plants animals from different countries
• Galapagos islands

Darwin's journey

• Species living here were unique to the islands but also similar to species on the mainland
• There were 14 finch species which all differed from one another in size, behaviour and beak shape. He observed that on each island the finches had a different beak shape. He also noticed that on each island, each type of finch had a different type of diet.

Species = A set of organisms that can create fertile offspring together.

fernandina

-> small fruit

santiago/san salvador

--> small seed

santa cruz

--> worms

pinta

--> large fruit

Which finch belongs to which island?

fernandina

-> small fruit

santiago/san salvador

--> small seed

santa cruz

--> worms

pinta

--> large fruit

Let's say all these finches now live on the same island, but there is a volcanic eruption leaving only hard seeds as a remaining food source. What would you expect to happen to the different finches on this island?

What does this tell us?

If there is huge disruption in an organism’s habitat, that the species who survive do so because they already posses an adaptation that enhances survival.

This is called natural selection.

natural selection 

--> every individual is unique (no clones)

--> differences in traits  are inheritable 

(Heredity) 

---> 1.  differences in inheritable traits 

i.e. there are green and brown beetles 

green beetles tend to get eaten by birds and 

survive to reproduce less often than brown beetles

and surviving brown beetles have brown baby

beetles 

the more advantageous brown colouration which allows the brown beetle to have more offspring becomes more common in the beetle population. 

If this process continues, eventually, all individuals in the population will be brown 

If we know that natural selection = the process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Then what do you think Artificial selection is?

What do you need for evolution to occur?

 (1) variation in traits among individuals

 (2) heritability of traits, 

(3) Natural selection and reproduction among individuals with advantageous traits, 

(4) finite resources leading to competition among individuals.

In the image you can see the evolutionary line of three finches.
At what point do we speak of new species?

1. When the different species live apart from each other
2. When the different species cannot create viable offspring together
3. When the different species all eat different types of food
4. From the moment different phenotypes started to appear

A certain type of finch has many different genotypes.

Does this finch species have a high or low chance of survival if the environment changes? Explain your answer.

It is important for organisms to produce offspring so that their species survives. But for the species to survive it is critical that the offspring survives. Therefore many plants and animals produce large numbers of offspring. A cod lays more than 3 million eggs. A poppy plant produces over 15.000 seeds. So why is the planet not over-run by cod fish and poppy plants?

Warfarin is a rat poison that was first used in the 1950’s. It was very effective in killing rats that were considered pests. However, nowadays many rat populations are unaffected. These ‘super rats’ are even resistant to large doses of Warfarin.

Explain how this happened using what you have learned this lesson.

According to biologist Armand Leroi, every human embryo has about 100 new mutations. But an embryo also inherits mutations from parents, grandparents and distant ancestors. As a result, an embryo has an average of 300 mutations that are more or less harmful (cause abnormalities or diseases). But not everyone is the same. Some have only 250. A very small number have as many as 340.

a)Explain how natural selection ensures that people do not get more and more harmful mutations.
b)Explain how our modern society influences natural selection.