EVOLUTION Who Says That Things Dont Change Over

EVOLUTION Who Says That Things Don’t Change Over Time?

How did livings things come to be? n. Write at least a ½ page essay on how you think living things came to be as they are today.

Lamark’s Evolution n n French naturalist Jean-Baptiste Lamarck was among the first scientists to recognize that living things have changed over time In 1809, Lamark published his hyptheses: n By selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.

CHARLES DARWIN n n English naturalist from the 1830’s. Went to the Galapagos Islands on the H. M. S. Beagle. observed that the finches on these islands were very similar to those in South America. From his studies he determined that organisms change over time and he wrote “The Origin of Species”.

CHARLES DARWIN n Darwin noticed that members of a species vary form one another n n We now call genetic variation Darwin noted that plant and animal breeders used heritable variation to improve crops and livestock n Termed this ARTIFICIAL SELECTION n Nature provided the variation and humans choose those variations they find useful

CHARLES DARWIN n Darwin was convinced artificial selection occurred naturally in nature n Darwin identified high birth rates and shortage of resources would eventually force organisms into competition for resources n Result: Struggle for Existence n Members of each species compete regularly for food, living space, and other nessecities of life

CHARLES DARWIN n n n A key factor in the struggle for existence was how well suited an organism is to its environment Darwin called the ability of an individual to survive and reproduce in its specific environment FITNESS Darwin proposed fitness is a result of ADAPTATION n Any inherited characteristic that increases an organism’s chance of survival

CHARLES DARWIN THEORY OF EVOLUTION n n 1) Individual organisms differ, and some variation is heritable 2) Organisms produce more offspring than can survive and many that survive do not reproduce 3) Each unique individual has different advantages and disadvantages. Each determines fitness which determines survival leading to natural selection. 4) Species alive today have descended with modification n Descent with Modificaiton: Each species has descended, with changes, from other species over time.

Evidence of Evolution n What is the evidence behind the Theory of Evolution: n Fossil records n DNA sequences and biological molecules n Embryology (Blastula/Blastophore) n Direct observation n Homologous and analogous structures n Vestigial structures

Fossil Record n n n The older the rocks, simpler the organisms. (No mammals, birds, reptiles, etc found) All old organisms aquatic. Lead to scientists belief life started in water or on ice. Changes in certain species can be observed in the fossil record over time. (For example: the horse)

DNA Sequences n n n All organisms have DNA. Organisms that look similar typically have very similar DNA sequences. The more the DNA sequences differ, the more the organisms appear to be different.

Embryology n n Embryos from all multicellular animals start off looking very similar and will then change during development. This evidence suggests that all animals had the same ancestor.

Direct Observation n n Organisms that have fast reproduction rate and life span will evolve much faster. (Ex. Bacteria) Within a few months to years, we can see that bacteria and viruses become resistant to our immune systems and to the medications that we take.

Homologous and Analogous Structures n n Homologous structures are similar structures with different functions. n Such as a human arm vs. bat wings Analogous structures have the same function but a different structure. n A bird wing vs. a butterfly wing

Vestigial Structures n These are structures that seem to have no distinct function within the body they are found in. n Example: The tailbone and the appendix (What do they do? )

What kind of scrutiny do scientists give a hypothesis before they make it a theory? Hypothesis n When an idea is young and not well tested, scientists call this idea a hypothesis. http: //superfrenchie. com/Pics/Blog/culture/e volution. jpg February 3 rd, 2008 n Hypothesis Rigorous testing Scientific laws Additional facts and Scientific theory observations that are rigorously scrutinized

What kind of scrutiny do scientists give a hypothesis before they make it a theory? n Theory n An idea will go under a great amount of testing and rigorous scrutiny n If the idea still holds up and the scientific community accepts it, it will become a theory. n If just one piece of evidence puts the idea into a question, it will never become a theory.

What kind of scrutiny do scientists give a hypothesis before they make it a theory? n Scientific Law n A scientific law is very similar to a scientific theory, but it describes something that is much more specific and narrow. n Can you name any other scientific laws?

How does evolution occur? n Step 1 - Replication: Organisms reproduce either asexually or sexually

How does evolution occur? n n Step 1 – Replication Step 2 - Variation: During reproduction, random changes (mutations!) can occur in the DNA that produce variation in the offspring. Sexual reproduction produces a greater variation in the species than asexual variation.

How does evolution occur? n n n Step 1 – Replication Step 2 – Variation Step 3 - Natural Selection: Over LONG periods of time, those individuals with characteristics that are best suited for the particular environment that they are living in will tend to be the ones that survive and pass on their genes to the next generation n Also known as survival of the fittest!!!

Causes of Natural Selection n n There are many things that organisms will struggle against. These are known as Selective Pressures. n These can change over time. Therefore, natural selection is an ongoing process. n n n Change in food source or a shortage of food Need for water Exposure to the environment/temperature Competition to attract a mate for reproduction Ability to move (to escape or catch a meal)

How does evolution occur? n Step 1 – Replication Step 2 – Variation Step 3 - Natural Selection n Step 4 - Formation of a new species: n n n Occasionally a group of organisms becomes separated from the rest of the species. The separate group may have different pressures on it, and the organisms will start to develop different characteristics than the original group; we call this a subspecies.

How does evolution occur? n Step 1 – Replication Step 2 – Variation Step 3 - Natural Selection n Step 4 - Formation of a new species: n n n If an animal is separated for a long time and changes a lot, they will no longer be able to successfully mate with the original group. At this point they would be considered a completely different species.

How much time are we talking about here? n n n The earth’s oldest rocks are about 4. 5 billion years old. Scientists estimated that life began 3. 7 billion years ago with prokaryotes. The oldest fossils are about 3. 5 billion years old. Eukaryotes came on the scene about 1. 5 billion years ago. Simple animals started to appear about 550 million years ago. More complex animals did not appear until 500 million years ago.

Four common misconceptions about evolution: n #1 - The “new” species are always “better than” (smarter, larger, or stronger) the ancestral species. n Correction: “new” species are better adapted for their particular environment. This does not always mean smarter, larger, or stronger. It could mean smaller, hairier, darker, lighter, slipperier, etc.

Four common misconceptions about evolution: n #2 - All organisms in the species evolve together. n Correction: If members of a species become separated geographically and are now in different environments, they can slowly evolve into 2 new species, each adapted to their own particular environment. (This is why there are monkeys AND humans. )

Four common misconceptions about evolution: n #3 – We cannot watch evolution “in action” n Correction: Actually we can see evolution occur in things that replicate extremely fast, like viruses and bacteria. We can also see that evolution exists by looking at the fossil record. Unfortunately, we cannot see complex organisms change during our lifetime. The time period is too short.

Four common misconceptions about evolution: n http: //wickedstageact 2. typepad. com/life_on_the_wicked_stage_/ Windows. Live. Writer/Dont. Drinkand. Playwith. Giraffes_EA 95/giraffe_01 %5 B 4%5 D. jpg 2/11/08 #4 - Evolution takes place as organisms acquire the characteristics to survive. (Lamarck, 1744 -1829) n Correction: characteristics are acquired by random chance when mutations occur. The favorable mutations will allow these organisms to be more successful at survival and also reproduction. The others will die off.

THINGS TO COME!!!! WHAT WILL FUTURE HUMANS LOOK LIKE? On your half sheet of paper, and on the back side, you can describe and/or draw what you think our species will eventually look like!!

BACK TO THE FUTURE? . . n n Will we be a blended coffee colored people where race is unimportant? Will we have better eyes and thicker wrists from our work with computers and other technological devices? Will the old science fiction image of big brained people with frail bodies come true? Will our future development and survival depend on how we respond to new bacterial and viral plagues?

BACK TO THE FUTURE? . . n n n What happens if we decide to have designer babies or stem cell cures that allow the weak to survive? Will the Neiman Theory of green skinned people come about someday when we can sit out in the sun and make our own food without other plants and animals? The future of man is dependent upon the choices we make and the changes we face in our environment and evolution.