Chapter 8 Developing a Theory of Evolution Evolution

Chapter 8 Developing a Theory of Evolution

Evolution In the biological sense is the process by which hereditary changes occur in one or more characteristics within a species over a long period of time - usually generations Evolution by natural selection is a scientific theory that explains how Earth’s large biodiversity developed in the past, and will continue in the future

8. 1 – Scientific Contributions How List do you learn more about something? 3 ways / things you do to better understand something …

Scientific Knowledge Scientific 1. 2. 3. knowledge develops as people Observe the world around them Ask questions And seek answers to their questions A scientific hypothesis – is a statement that provides 1 possible answer to a question or observation

Hypothesis Hypotheses (plural) are tested to determine the validity of an answer, usually through: Experiments v Observation v Creating models from data v Or a combination of these ways v Hypotheses that consistently lead to the same answer are sometimes made into a general statement that explains the phenomenon These statements are called: Scientific Theory

So … Where did we come from?

Where did we come from? This question has been asked and debated for thousands of years Many of the earliest ideas were influenced by religion and philosophy However, with time, scientist began to study this idea and came up with something else

George-Louis Leclerc, Comte de Buffon (1707 – 1788) A French naturalist was the first to note similarities between humans and apes, and hypothesize that they may have a common ancestor – suggesting that the species have changed over time He also believed that the world was much older than originally thought to be at the time

Evolution in the 1830’s After George-Louis Leclerc, Comte de Buffon’s theory, other scholars from a variety of specialties – paleontology, geography, geology, and biology, began to share their ideas to explain how life could change with time

The big bang theory? Video: https: //www. youtube. com/watch? v=Nzb. DI 1 M Alhk

The Science of Paleontology Fossils are important to the study of evolution A fossil – is the preserved remains of a once living organisms Fossils can be preserved in amber, permafrost, dry caves, and even rock Mary Anning became respected in the scientific world for her important work with fossils, as she discovered the 1 st plesiosaur, an aquatic reptile

The Science of Paleontology Georges Cuvier – another French Naturalist, is known for his work in developing the science of Paleontology: the study of ancient life through the examination of fossils

The Science of Paleontology Cuvier found that each layer of rock, called Stratum, is characterized by a unique group of fossil species, where the deeper (older) the layer of rock were, the more different they became

Catastrophism Based on his observations, Cuvier proposed that the Earth had experienced many destructive natural events in the past, like floods and volcanic eruptions He called these “events, ” Revolutions This phenomenon = Catastrophism – where these “revolutions” or catastrophes destroyed species living in a particular region, allowing species from neighbouring regions to repopulate the area This idea helped explain the appearance of fossils that did not exist anymore

Charles Lyell (1797 – 1875) REJECTED Cuvier’s theory of Catastrophism, and believed that geological processes operated at the same rates in the past, just as they do now This process is called uniformitarianism He also theorized that slow, subtle processes could happen over a long period of time – and could result in substantial changes For example – the forces that build and erode mountains, just as floods in the past had no more power than they do today

Jean – Baptiste Lamarck By comparing current species of animals with fossils, Lamarck discovered “lines of descent” / progression – where a series of fossils led to a modern species. He thought that “species increased in complexity over time, until they reached their level of perfection” Lamarck hypothesized that the organisms would become progressively better adapted to their environments

Jean – Baptiste Lamarck For example – giraffes stretch their necks to eat the leaves on top of the trees, over time they would pass on this trait to their offspring, where all giraffes would be able to eat from the tops of trees This idea is known as: the inheritance of acquired characteristics

Jean – Baptiste Lamarck also suggested that body parts that were not used would eventually disappear This idea is called use and disuse

Jean – Baptiste Lamarck provided a hypothesis for how the inheritance of characteristics from one generation to the next occurs He also noted that an organism's adaptations to the environment result in characteristics that could be inherited to their offspring These ideas were very controversial at the time, yet posed as a stepping stone for others like Charles Darwin to study inheritance in more detail

Charles Darwin (1809 – 1882) When he was 22, Darwin left England to map out South America In his voyage, he noted many observations and questions arising from what he witnessed in the natural history of these places This led to his Theory of Evolution – by natural selection http: //www. sciencechanne l. com/video-topics/earthscience/galapagosbeyond-darwin-charlesdarwin. htm

Darwin’s Observations & Questions (p. 329) Observations Questions If all organisms originated in their present form during a single event, Darwin wondered, why was there a distinct clustering of similar organisms in different regions of the world? Why were all types of organisms not randomly distributed Why would living and fossilized organisms that look similar found in the same region Why did the Galapagos species resemble the organisms adjacent to the South American coastline so much? Why was there so much diversity of species in such a small area? Could these species have been modified from an ancestral form that arrived on the Galapagos Island after the islands formed? Could a process similar to artificial selection also operate in nature?

Darwin, Wallace, & Theory of Evolution by Natural Selection After Darwin’s trip, he began to come up with some answers to his questions He organized this and the observations of others into a theory that explained how species changed over time Darwin and Wallace (British Naturalist) accepted that populations change as time went on, but they were unclear as to HOW this happened

Darwin, Wallace, & Theory of Evolution by Natural Selection The work of other researchers gave light to the idea that individuals with traits that helped them survive in their local environments were more likely to survive to pass on these traits to their offspring Where competition for limited resources between individuals of the same species would select for individuals with favourable traits – that would increase their chances of surviving and reproduce Thus, a growing amount of the population as a whole would have these traits in later generations

Darwin, Wallace, & Theory of Evolution by Natural Selection This is the idea of Survival of the Fittest Darwin called this process Natural Selection Darwin proposed that all life descended from some unknown organism As descendants of this organism spread out over different habitats during the millennia, they developed adaptations that helped them survive better

Darwin, Wallace, & Theory of Evolution by Natural Selection Darwin’s ideas of Survival of the fittest: 1. Organisms produce more offspring than can survive. Thus, organisms compete for limited resources 2. Individuals of a population have a lot of variation between them, and is inherited 3. Individuals that are better suited to local conditions survive and reproduce 4. Processes for change are slow and gradual

Descent with Modification Darwin did not use the word Evolution in his findings, as this implied progress in a species Natural Selection does not show progress, it is random with no certain direction Instead, he would say and organism “descent with modification” – as progressed as a means to survive the local environment at one time

TASK Draw out a Timeline of the events that have taken place in history that have led up to the Theory of Evolution

Natural Selection – Gizmo

Section 8. 2 Sources of Evidence for Evolution

Introduction Darwin was not the only person to conclude that life has changed over long periods of time, but he was the first person to publish these ideas

1. Fossils: Evidence of Life Sediment Rock with fossils provides a fossil record of the history of life by showing the kinds of species that were alive in the past

Geologic time scale (p. 333)

1. Evidence from the Fossil Record The A. fossil record provides evidence of: Fossils found in the younger layers (closer to the top) are more similar to species alive today than those fossils closer to the bottom. Ø This is seen when looking at the evolution of horses over time

1. Evidence from the Fossil Record B. Fossils appear in chronological order within the layers of rock – where ancestors for a species are found in older rock C. Not all organisms appear in the fossil record at the same time Ø Ø Example – fossil history says that fish are the oldest vertebrates, following amphibians, reptiles and mammals, etc. These changes were slow growing, and occurred over millions of years!

1. Evidence from Transitional Fossils The original fossil record gave only scattered pieces of ancestral beings This leaves scientists wondering about the gaps between the pieces that have not been discovered Ongoing discoveries have lead to the identification of Transition Fossils o o These fossils show intermediate links between groups of organisms, with a common ancestor This is important when the descendant group is sharply differentiated by gross anatomy and mode of living from the ancestral group.

1. Evidence from Transitional Fossils However, as organisms developed with time, they adapted to their environment Structures that are reduced forms of a structure that were at one point functional in the organisms’ ancestors are called vestigial structures

1. Evidence from Transitional Fossils Use this knowledge and information from the textbook to explain the relationship between Archaeopteryx & the modern toothed whale (p. 335)

2. Evidence from Biogeography – is the study of past and present geographical distribution of organisms Darwin’s theories were based on his observations and Biogeography supports his hypothesis that species evolve in 1 location and then spread out to other areas

2. Evidence from Biogeography Some A. examples of Biogeography include: Geographically close environments (like the desert and rainforest in Africa) are more likely to be populated by related species than locations that may be separate but similar in environment (like the desert in Africa vs. desert in Australia)

2. Evidence from Biogeography Some examples of Biogeography include: Animals found on island often resemble animals found on the closest continent B. Ø This suggests that animals on the island would have evolved from mainland animals, as the population would have adapted with time

2. Evidence from Biogeography Some C. examples of Biogeography include: Fossils of the same species can be found on the coastline of neighbouring continents Ø This is supported by the idea the at one time (510 million years ago) continents like Africa and South America were joined in a “supercontinent” called Gondwana – where they slowly move apart over time

2. Evidence from Biogeography Some D. examples of Biogeography include: Closely related species are almost NEVER found in exactly the same location or habitat

3. Evidence of Anatomy Vertebrates forelimbs can be used for many things – like flying, running, and swimming Despite their different functions, all vertebrate forelimbs contain the SAME set of BONES, organized in similar ways This is due to a common ancestor

3. Evidence of Anatomy Homologous structures – have similar elements and origin, but may have a different function Again, they are common because they were inherited from a common ancestor Often, Ø they are similar in function too Lower limbs of a frog and horse perform the same function to those of a human (movement on land)

3. Homologous Hair In mammals, hair is homologous Complete activity 8. 2 (p. 337) and compare the various functions of hair in mammals

4. Evidence from Embryology is the study of early, pre-birth stages of an organisms development It is used to determine evolutionary relationships between animals Embryos of different organisms exhibit similar stages of embryonic development Where, at certain stages in the development of the embryo, the similarities between vertebrates can be seem more clearly than differences

5. Evidence from DNA Recall – evolutionary relationships between species are reflected in their DNA Since DNA carries genetic info, scientists can determine how closely 2 organisms are related by comparing their DNA If 2 species have SIMILAR patterns in their DNA, this indicated that these DNA sequences would have been inherited from a common ancestor

5. Evidence from DNA The use of modern technology has led to many discoveries that support Darwin’s theory Scientists o o now know: How species pass on their traits to their offspring How genes for these traits can change by mutation

5. Evidence from DNA Thus, genetic evidence and our understanding of heredity and mutations support hypothesis that come from observations of: Fossils Anatomy Biogeography Embryology and DNA relationships

Review 5 evidences of Evolution Video: http: //www. sophia. org/tutorials/5 -evidences-ofevolution https: //www. youtube. com/watch? v=c. C 8 k 2 Sb 1 o. Q 8

Review Take some time to complete the given worksheets to reinforce this information