Evolution: Grade 12 Introduction

Distinguish between a hypothesis and a theory Hipothesis consists of the following key concepts – Dependent variable – Independent variable – relationship between the two variables – Testable Summary: An educated statement/ guess (two variables) which is testable NOT A QUESTION

During an investigation which is testing your hypothesis, the findings or results, might end in one of the following: Your hypothesis is... 1.not rejected / accepted 2.rejected, or 3.adapted (create new or more questions) NOT PROVEN

Constructing new scientific knowledge A number of not rejected, interrelated hypotheses, which provide usually complex inferences and explanations … construct new scientific knowledge Leads to theories

Distinguish between a hypothesis and a theory Theory consists of the following key concepts – Overarching explanations of interrelated hypotheses that have been tested and not rejected/accepted –These well-substantiated explanations incorporate facts, laws, inferences, and tested hypotheses –Allow scientists to make valid predictions/ conclusions.

A theory deals mainly … of how aspects (processes and/or mechanisms in life) in the natural world work.

Some basic definitions Fact: an observation that has been repeatedly confirmed / verified over years Law: a descriptive generalization about how the physical world behaves under certain conditions Hypothesis: a testable statement that can be used to build inferences and explanations

EVOLUTION: Content History Definition Natural Selection Spesiation Bewyse vir evolusie –Fossil records - Transitional stage – Modification from ancestor – Biogeography –Genetics

History of the earlier development of the evolution theory Four persons have played an important role in the development of the earlier evolution theory, namely, 1.Erasmus Darwin’s ideas ( Grand father of Charles): All life developed from simple forms There are similarities amongst various organisms Artificial selection and metamorphosis showed how changes may have occurred

History: Lamarck 2.Jean Baptiste de Lamarck (1744–1829) His two ideas: 1.Use and disuse Changes in the environment create new needs that cause organisms to modify their existing organs to meet the need. Repeated use of the organ would cause it to enlarge and become more efficient. Disuse of a organ would cause it to degenerate

2.Inheritance of modified characteristics The modification an organism acquired during its life time could be pass on to its offspring. History: Lamarck

Lamarck: Examples Examples of the application of Lamarck’s ideas (e.g. Long neck of the giraffe or the legs of a snake)

Misuse Legs of snake disappeared because it did not use them in its gliding movement; Their bodies became thin and long to allow them to crawl through narrow spaces

More examples of Lamarck’s ideas Penguins without wings Ducks stretch their toes apart to achieve an efficient swimming stroke and the skin between the toes also became stretched

LamarckDarwin Individuals want to adapt to the environment (determinism, internal drive) No drive to change (no internal drive) Individuals in population change Change because of environmental factors Variation because individual change Offspring showed variation when produced Change acquired during life time inherited from parent to offspring Natural selection – favourable characteristics inherited from parents to offspring DIFFERENCES

Lamarck: Rejected Reasons for Lamarck’s theory being rejected: 1.Theory is deterministic. He imagined that all organisms had an internal drive to ascend the ladder of development during evolution. He did not think of evolution in a tree-like form.

Lamarck: Rejected (cont) Reasons for Lamarck’s theory being rejected: 2.Inheritance of acquired characteristics can’t take place. No change to its HERITABLE MATERIAL. No genetic basis for this. 3.Environmental factors only can`t cause evolution – variation must be present as well / natural selection

History: Charles Darwin 3Charles Darwin ( ) Theory of evolution by natural selection under the following captions: Darwin’s 5-year voyage around the world in the HMS Beagle, collecting specimens and keeping notes of plants, animals seen and geography of countries visited. –The historical development. In 1858 he was aware of Wallace’s work. Afraid to publish his ideas, because people might think that he has stolen Wallace’s ideas. –Darwin’s article together with Wallace’s article were presented during the “Linnaean Society conference” at 1 July –Publication of “On the Origin of the Species” in 1859

History: Charles Darwin (cont.) The observations on which Darwin based his theory: Organisms of a species produce a large number of offspring The offspring show a great deal of variation Of the large number of offspring produced, only a few survive Characteristics are inherited from surviving parents to offspring

History: Wallace 4 Alfred Wallace ( ) Wallace and Charles Darwin have independently described natural selection as an explanation for evolution.