Biology 11 Name: ____________________ Block: ___ Date: _____________

Chap 15 - Darwin’s Theory of Evolution (Natural Selection)

Introduction:We, humans, share the earth with millions of other living species. The variety of living things is called _____________________.

What is biodiversity? Watch ....

What is the scientific explanation for biodiversity? _____________________________!!

(Recall – A theory in science = a collection of scientific facts, observations, and hypotheses that have been tested and proven over and over again to be true.)

What is The Theory of Evolution? Definition of Evolution – (a) ______________________________________________________________________ of a population(b) ________________________________________________________diversity (or

extinction).

Evolution is fundamental to the study of biology at ALL levels – from molecules to ecosystems

To help understand Evolution, let’s take a look at a bit of history ....

Early Concepts of Evolution

Greeks = Plato & Aristotle believed in ______________- In which a separate creation of each type of organism at the beginning of

the world by a ____________________. World age estimated to be about 6000 years old.

In the 1700’s many fossils were being discovered and the geology of the world was challenging these traditional ideas.

Buffon (1707 – 1788)- to understand the world, he needed to understand its ___________. He

looked to Science, not _______________. Proposed that a _________ _______________________ became the planets of the solar system and created the matter that would become land and oceans.

- Estimated the world was _____________ years old- He thought life can be divided into a number of distinct types or “_________

_____” formed by the “__________” that are available in a given area. During migrations, life changed. As species moved to new habitats, there would be a new supply of organic particles in the new area, so they can make a ____________________. His ideas were wrong, but they did account for the geographical distribution of similar species found around the world.

- For example – the 3 animals pictured on the left >>>

Cuvier (1769 – 1832) – believed in _______________- studied fossils. Instead of believing that fossils of elephants near Paris were related to fossil elephants found in Siberia, Africa and India, he proposed they were different and distinctly separate species. He proposed that ________________________________________(i.e. catastophes) made species go extinct. From the void, new species would be created.

Hutton and Lyell (late 1785 – 1835) – believed in _____________________Earth was transformed not by catastrophes but by imperceptibly _______ _________. Natural geological forces (like wind, rain erode mountains, eroded sediments form into layers of rock, which can later be lifted above sea level ... ) take place over extremely long periods of time and cause slow and___________________________. Earth was millions, not thousands of years old.

Lamarck (1744 – 1829) – inheritance of _______________________

- first scientist to recognize ___________________________ over time

- HOW it happened was ________

-Lamarck’s theory = ________________________________-Lamarck relied on 3 incorrect assumptions:

1. An organism has a ____________ ___ _________§ Organisms have an inborn desire to better

themselves and become more fit for their environments.

2. Be engaging in certain behaviour. ______or _______§ Organisms can alter their shape by using their

bodies in new ways.3. These ____________________ can be passed on to the

next generations§ Acquired characteristics are inherited.

Example – Giraffe on the right - uses his neck to reach higher and higher trees. Because of this, future generation have longer necks.- Herons don’t want to get their thighs wet, so they stretch their legs. Future generations have longer legs.

- Giraffe on the left - only eats short trees, he doesn’t use his neck (disuse). So, next generation has a short neck.- Herons who live/eat/hunt in shallower water, don’t need or stretch for longer legs. Future generations have shorter legs.

Charles Darwin (1809 – 1882) –Set sail in 1831 and spent five years sailing around the world, collecting specimens and making many observations. Where did the HMS Beagle go?

When Darwin returned to England, reviewing his observations about the plants, animals he saw around the world and information from other scientists, Darwin made 6 key observations that shaped and developed his theory of descent with modification (known in modern day terms as the theory of evolution). (Source: Textbook - Chapters 15.2 – 15.3)

1) The _______________ ________ – millions not thousands of years old AND the ____________ ____________________________operate in the present. ( (Lyell and Hutton)

2) Humans produced __________ ______________than could survive. If populations continued to grow unchecked, there would not be enough living space or food for everyone. ____________, __________ and __________ helped to control the population size. (Malthus)

3)

4) There is ____________ in nature. No ______________________________________________ (unless they are identical twins). E.g. starfish, leaves, high school students, dogs, cats etc. New variations are passed onto the next generation

5) Farmers would look at their plants and livestock. They ________________________the specific traits they are looking for and then_______________________________. This process is called artificial selection. Only certain individuals of a population are selected to produce new individuals and the process is controlled by humans.

6) The ____________________ (biome, ecosystem, habitat) animals live AND the animals _______________ impact whether they will ________________________or not.

These observations led to Darwin’s theory of evolution (Chapter 15.3). Darwin stated:1) All organisms are descended from _____________species that are different from __________

species.

2) _______________ selection provided a mechanism for this evolutionary change.

Example: Camels in Norway have not problems surviving the cold. Why?

-thick wooley coat

Lamark’s was the first to develop a _______________________and, although he was wrong, he recognized that organisms are _________________________________.

Natural Selection is the process by which individuals are ______________(or adapted) to their environment survive and reproduce most successfully. This is also called ____________________.

Darwin’s idea about evolution by natural selection has 5 key parts. It is simple, but often misunderstood.

1. There is variation ____________ among members of the ____________ speciesa. Look around the room, every student is different. But we are all still part of the same

species = i.e. humans.b. Look at dogs – all dogs are dogs – but there is a lot of variety in height, weight, colour,

fur/hair, etc.

2. Organisms produce _________ ______________than can survive. Darwin called this overproduction. And, of the organisms that survive, not all get to ___________.

a. Since the environment can’t support unlimited population growth, not all individuals get to reproduce.

3. Because _______ organisms are produced than can survive, they ____________ for limited resources. E.g. food, water, living space

NOTE: Competition = struggle for existence. An _________________________________ _________________________________ of evolution.

4. Each organism has different advantages and disadvantages (i.e. __________________ in the struggle for existence. For example:

a. The predators that are faster or have a particular way of ensnaring their prey can catch more prey.

b. The prey that are faster or better camouflaged or better protected are less likely to be caught and/or eaten and will survive to reproduce.

c. As a result, individuals ___________ _______________for their environment survive and _____________.

Fitness = the ability of an organism to survive AND reproduce in its particular environment.

Fitness is a direct result of the __________________________________________that the organism has that allows those organisms to survive and reproduce

- The concept of fitness is central to the ___________________________________________ selectiono Individuals that are not well suited to their environment i.e. have _____________of fitness die

or have few offspring. o Individuals that are better suited to their environment i.e. have adaptations that enable fitness

– survive and reproduce ________________________= survival of the fittest- To Darwin, survival of the fittest = _______________________

- Darwin used the term natural selection because of its similarities to _________________selection. o In both artificial and natural selection, only ________________of a population produce new

individuals. o Artificial selection in farming involves _________________or direction. Natural selection takes

place without human intervention.o In natural selection, the traits being selected, and therefore increasing in frequency over time,

contribute to an organism’s fitness in its environment.

5. So, over time, it’s the_______________________, characteristics and traits, the ones that allow the organism to survive and reproduce, that get___________________________________. i.e. heredity.

Natural selection results in changes in the inherited characteristics of a population. Over numerous generations, __________________ by the accumulation of variations inherited from their ancestors

In conclusion, Darwin proposed “Descent with modification” (vs evolution)- All organisms are related __________________________ __________________ that lived in the past.

Over long periods of time, natural selection produces individuals with different structures, niches, habitats, physiological processes, and/or behaviours that look different today versus their ancestors.

- Over evolutionary time, the descendants from the common ancestor ______________(inherited) diverse modifications or ______________that allow them to survive and reproduce in_______________________.

Consider an example:a. There is variation in __________

i. For example, there may be some beetles that are green and some that are brown

b. There is a struggle to___________.i. Since the environment can’t support unlimited population growth,

not all individuals will survive and reproduce AND.ii. Beetles are a source of food to birds. Birds eat the beetles.

c. There is _______________i. The surviving beetles have baby beetles. Brown beetles will have

brown beetle babies and green beetles will have green beetle babies.

d. There is the _______________ the beetles live in.i. If the beetle lives mostly on brown soil – which beetles get eaten

more often by the birds? The green beetles. As the green beetles are eaten more than the brown beetles there will be more brown beetle survivors.

ii. The end result? The brown beetle is “_________” and becomes more common than the green beetle. With more generations of beetles being eaten and reproducing there will eventually be no more green beetles. (The green beetle had________________.)

NOW, go back to the pictures of Lamarck’s giraffes. Applying Darwin’s principles of natural selection and evolution, what is a more likely explanation for a giraffe’s long neck?