What does each picture show? What is the same in the pictures?

The Theories of Evolution The Theories of Evolution

Species change over time!!!Species change over time!!!

K-W-LK-W-L

– Write everything you already know about evolution in the K column

– Write everything want to know about evolution in the W column

– Leave the L column blank for know, but fill it in each day at the end of class

What Do We Know?What Do We Know?

• Evolutionary theory helps biologists understand how fossils fit into life’s history and how natural selection shapes our world today.

• Evolution explains how bacteria became resistant to antibiotics, how new diseases arise, and how insects become resistant to pesticides.

• Modern genetics is helping biologists determine the relationships among the different groups of organisms on Earth.

What We Want to Learn?What We Want to Learn?

• Can evolutionary theory help predict which strains of diseases, such as influenza and tuberculosis, will be most deadly next year?

• What will the study of fossils and genes reveal about the early evolution of the major groups of plants and animals?

• Will studying the mass extinctions of the past help scientists find ways to protect biodiversity today?

• What new organism will be discovered as a result of the current efforts to classify and catlog all of life’s diversity?

To Summarize it up…To Summarize it up…

• Species evolve (change) over time. • Evolution is the consequence of the interactions

of – (1) the potential for a species to increase its numbers– (2) the genetic variability of offspring due to mutation

and recombination of genes– (3) a finite supply of the resources required for life – (4) the ensuing selection by the environment of those

offspring better able to survive and leave offspring

Evolutionary FoundationEvolutionary Foundation

• Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.

• Lamarck proposed that 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 = Adaptation

• Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

Introducing Evolutionary TheoryIntroducing Evolutionary Theory

• We share Earth with millions of other organisms (variety of living things) = Biological Diversity– How is everything so different?

• Evolution = change over time leading to modern organisms that have descended from ancient organisms

• Theory = well-supported testable explanation of phenomena that have occurred in the natural world

Introducing… Charles Darwin!Introducing… Charles Darwin!

• In 1831, Darwin set sail on the Beagle for a voyage around the world

• During his travel, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time = The Theory of Evolution

• Darwin used these observations to scientifically explain the diversity of life on this planet.

Darwin’s observationsDarwin’s observations

• Darwin was interested in the diversity of organisms in specific areas and the specific locations species inhabited

– How were there so many different organisms and why do they live in specific areas?

• He also found fossils of the past that resembled present day organisms

– Why did they disappeared and were they related?

• He was fascinated by the differences on the Galapagos islands

– Why were these close islands inhabited by similar organisms that appeared slightly different?

The Galapagos IslandsThe Galapagos Islands

• Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands.– Did these species evolve from a common ancestor

after being isolated to different islands needing different survival skills?

The Controversy The Controversy

• Darwin brought some specimens back and studied them, soon realizing that they were separate species that did not exist anywhere else in the world!– These species were clearly different from mainland

species and from one another.

• In 1859, Darwin published a book: On the Origin of Species about species diversity and evolution (natural selection) that would change how we view the world!

Natural Variation & Artificial SelectionNatural Variation & Artificial Selection

• Natural Variation = differences among individuals of a species– Variations can be inherited from one generation to

the next

• Selective breeding = humans select desirable traits and breed based on natural variation (to improve crops/farms) – Darwin called this artificial selection = nature

provides variation among different organisms, and humans select variations they found useful.

Evolution by Natural Selection

• Living things evolve as the result of:– The struggle for existence– The survival of the fittest– The descent with modification

Struggle for ExistenceStruggle for Existence• Darwin was convinced artificial selection worked in

nature as the result of overproduction and competition for resources = struggle for existence (members of each species compete regularly to obtain food, living space, and other necessities of life)– Depends on an individual’s ability to survive and

reproduce = fitness– Fitness results from adaptations = inherited

characteristics that increase an organism’s chance of survival

– = “Survival of the Fittest!”

Natural SelectionNatural Selection

• Survival of the fittest = Natural Selection– Traits are being selected and increasing over

time (over many generations without human influences)

• Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.

Descent with Modification

• Over time, natural selection produces organisms with different structures or functions resulting in species that look different from their ancestors– Each living species has

descended with changes from other species over time = Descent with Modification

• Then, all living things must be related!– There’s a common ancestor

of all living things = Common Descent

Evidence of EvolutionEvidence of Evolution

• Living things have been evolving on Earth for millions of years. Evidence of this process could be found in:– The fossil record – The geographical distribution of living species– Homologous structures of living organisms – Similarities in development

Fossil Record

• Remember: Fossils are the remains of ancient life and different layers of rock were formed at different times.

• Fossils in different layers of rock are evidence of the gradual change over time (different species appeared, lived for a time, and then vanished)

Geographic Distribution

• Populations in different places adapted to different environments… different species descended with modification from a common ancestor.

• Different species living in similar environments in different parts of the world sometimes have similar structures and functions because they experienced similar pressures of natural selection

Homologous Structures

• Some vertebrates have similar bone structures that develop from a specific group of cells in an embryo, but the structures adapted different functions so the organism can survive in different environments providing evidence of descent with modification from common ancestors

• Homologous Structures = they appear and function differently, but develop from the same embryonic tissues

• Some homologous structures provide little or no function in some organisms = vestigial organs

Similarities in Development

• Embryos of many vertebrates look very similar in the early stages of development.

• The same groups of embryonic cells develop in the same order and in similar patterns producing homologous structures

Summary of Darwin’s TheorySummary of Darwin’s Theory• Individual organisms in nature differ, and some variation

is inherited• Organisms in nature produce more offspring than can

survive and reproduce• Members of each species compete for limited resources• Unique organisms have different advantages and

disadvantages in the struggle for existence• Individuals best suited to their environment survive

and reproduce, passing the characteristic to their offspring. Individuals without the characteristic die

• Species change over time due to natural selection… new species arise and others disappear

• Species alive today have descended with modification from species of the past

• All organisms on Earth are united by a common descent