Evolution

Life from Life • Spontaneous Generation: the idea that living organisms can suddenly

appear from non-living objects.• Ex. Ancient Egyptians believed that all living organisms came from

the Nile River.

Spontaneous Generation Experiments• Franciscio Redi (1626-1697): Attempted to disprove the idea of

spontaneous generation.

Spontaneous Generation Experiments• John Needham (1713-1781): Defended spontaneous generation. (He

was wrong!)

Spontaneous Generation Experiments• Lazzaro Spallanzani (1729-1799): He criticized Needham’s work and

conducted further experiments to debunk the spontaneous generation idea.

Spontaneous Generation Experiments• Louis Pasteur (1822-1895): He modified the broth experiments one

last time by using a flask with a curved neck. Pasteur was finally able to demonstrate that life only came from other life.• Biogenesis: the idea that only living organisms can give rise to other

living organisms.

Evolution• Evolution: the simplest definition is change over time.

• Types of Evolution• 1. Chemical Evolution: attempts to describe how complex biomolecules

formed from simple inorganic and organic molecules.• Stanley L. Miller & Harold C. Urey conducted an experiment to try and show

this. They were able to demonstrate the spontaneous emergence of organic amino acids.

Evolution• Sidney w. Fox (1912-1998): His experiment used a special high temp.

oven to dry amino acid samples and hot lava mixed with amino acids. He noticed the amino acids naturally tended to crystallize into long stable chains. He called these “proteinoids.” • Proteinoids are protein-like molecules made inorganically that contain

most of the 20 known modern amino acids. • In other experiments, he then showed how these proteinoids formed

into microspheres that he called protobionts.• Protobionts are seen as the precursor to cells.

Evolution• Types of Evolution• 2. Organic Evolution: the continuous change of living organisms. • Scientists still do not know how living things first evolved. Remember that the

environment was very different that today, with little oxygen in the atmosphere.

Evolution• Heterotroph Hypothesis: The idea that tiny cells did not use oxygen

and consumed biomolecules. (Anaerobic heterotrophs)• The idea is that these organisms learned to capture and use light

energy and thus developed into photosynthetic autotrophs. These organisms would have made oxygen the same as plants do today.

History of Organic Evolution • Charles Darwin (1809-1882): Born in England, attended Cambridge to

train for the ministry after a short period of study at medical school. • Darwin went on a 5 year voyage on the ship H.M.S. Beagle.• He observed fossils on many different continents and observed and

collected organisms from all around the globe.• One place of particular interest was the Galapagos Islands off the

coast of South America.

History of Organic Evolution• Darwin noticed that all the organisms on this island looked very

similar to the organisms on the South American continent, especially the finches (birds). • The finches were all about the same size and color. However, the

difference was in the beaks and in what they ate. Some ate insects, others seeds, others egg yolks and blood, and so on. • The finches were very diverse. • Note: The existence of DNA was NOT known at this time.

History of Organic Evolution• In 1859, after 20 years of study, Darwin published his book, The Origin

of Species.

• Darwin developed the theory of Natural Selection.• Natural selection is based on the idea that environmental pressures

can change how an organism interacts with its environment.

Organic Evolution• Darwin’s finches did NOT change overnight but, rather, over many,

many generations.• Those born with longer, sharper beaks naturally had access to food

that other finches did not. Then they had more offspring because they were healthier and survived longer and reproduced more. Therefore, their advantageous trait is passed on to their offspring. This is an example of how natural selection works.

Darwin Didn’t Do It Alone• Jean-Baptiste Lamarck (1744-1829): one of the first people to

propose the idea that living organisms can change. • However, Lamarck thought acquired traits could be passed on. This is

wrong. Ex. If you dye your hair blonde, you do not pass on blonde hair to your children.

Darwin Didn’t Do It Alone• Charlies Lyell (1797-1875): a geologist that said the earth’s processes

happen very slowly over a long period of time. This is called uniformitarianism.• Catastrophism is the idea that huge natural disasters dominated

Earth’s history and led to the development of all landforms.• Lyell’s ideas were important to Darwin because they helped him to

see the earth as very old and that it would take a very long time for things to change.

Darwin Didn’t Do It Alone• Thomas Malthus (1766-1834): a social economist who wrote about

human populations. He recognized that humans produce as many offspring as they can, and in the end, there are environmental limiting factors that determine which offspring survive to adulthood. • This idea helped Darwin appreciate the importance of competition in

wild populations and led him to the idea of natural selection.

Darwin Didn’t Do It Alone• Alfred Russel Wallace (1823-1913): He was a colleague of Darwin’s

and cited as a co-founder to the evolutionary theory. He collected and studied many different organisms and sent some to Darwin, who used them to support his theory of natural selection.

Natural Selection• Natural Selection states that organisms best suited to the

environment are the ones most likely to survive and reproduce.

Natural Selection Important Points• 1. Resources are limited in all environments. This creates competition

amongst living things.• 2. Most organisms have more offspring than the environment can

support. Ex. A fish lays thousands of eggs, or one tree produces millions of seeds.• 3. There is natural variation within a population. Ex. Not all moths are

the exact same color, or all humans are not the same height.• 4. Natural selection is always taking place. Fitness is the ability of an

organisms to live, survive, and reproduce in that environment.

Natural Selection (AKA Survival of the Fittest)• The fittest organisms will survive and reproduce, passing on their

traits. • This does not always mean the fastest or strongest. Fittest may just

mean the beak shape of a bird allows it more food options. • Unfavorable traits will eventually be lost.

Natural Selection & Diversity• Organisms are different, even if they are the same species.• However, when an organism becomes very different from its original

state, it may be classified as a new species. This is called speciation.

Natural Selection & Diversity• Biologists agree that in order for a population to be considered a

distinct species, it must be geographically and sexually isolated from other closely related organisms. • Species: a group of similar organisms living in the same geographic

area, that can interbreed to produce fertile offspring.• -A mule is not considered a species because it is not fertile, and therefore,

cannot interbreed. Same goes for a liger.

Graphic Genetic Variations

Graphic Genetic Variations• Stabilizing Selection: this occurs when an environmental change acts

to eliminate the extremes in a population.

Graphic Genetic Variation• Directional Selection: occurs in either direction, shifting the

population toward a new norm. This is often how new species are formed.

Graphic Genetic Variation• Disruptive Selection: occurs when an environmental change acts on

the most common variety. In this type, two new distinct varieties appear.

Mutations• Mutations: random changes in DNA that act as further mechanisms

for evolution. These changes result in a variation of traits that are then passed from one generation to another.• Mutations can be beneficial, neutral, or harmful to an organism. • Beneficial mutations can make an organism more fit, which leads to

longer survival and more reproduction. The mutation is now a part of the population’s gene pool.

Gene Flow• Gene Flow: the exchange of genes between two populations. It most

often occurs due to migration or movement of the organisms. • Individuals that leave a population take their genes with them,

effectively shrinking the gene pool of the larger population and isolating themselves. This would have happened to the finches and other organisms that migrated to the Galapagos Islands from South America.

Genetic Drift• Genetic Drift: the change in frequency of alleles in a population. • It provides random changes in the occurrence of genes through chance

events. • Small populations are more affected by genetic drift.• Bottlenecking: this can occur if a large number of the population is killed

because of disease, starvation, natural disaster, etc. The large population is reduced to a few individuals, and the genes of later generations become very similar. • Bottlenecking can lead to the quick development of new species, or it can

lead to a species going extinct.• Inbreeding between these few individuals lead to populations that have very

few genetic differences, and thus, more susceptible to diseases.

Behavioral Animal Adaptation• Animals use behavioral adaptation for survival and reproduction.• Territoriality: a behavioral adaptation that ensures adequate space

and resources for reproduction. Ex. Male elephant seals battle for specific beach territories during breeding season.

Behavioral Animal Adaptation• Courting Behavior: a behavioral adaptation that helps to ensure

beneficial genes are passed along to offspring. • Mates that can build the best nests, sing exuberant mating calls, or

have the brightest colors are healthy and strong and will likely produce the strongest offspring. Ex. Lightning bugs display bright lights to attract mates, birds build nests, do dances, sing songs, and grow specialized feathers.

Behavioral Animal Adaptation• Animals, like plants, follow circadian rhythms, which are innate

behavior cycles. • Some animals are active during the day. They are called diurnal.• Some animals are active at night. They are called nocturnal. Ex. Bats

and raccoons. • Hibernation: A dormancy during cold periods.• Dormancy: a period of biological rest or inactivity. Ex. Breathing,

metabolism, and body temp. decline.

Behavioral Animal Adaptation• Estivation: dormancy during hot or dry periods. Ex. Frogs, snails, and

tortoises estivate to avoid extremely hot or dry seasons.• Migrate: moving to a new location in response to weather changes,

to stay close to food and water, or follow potential mates.• Some animals, like geese, use the same migration routes every year.

Patterns of Evolution• Gradualism: species change slowly over many generations.• In this model, a particular trait continuously changes in regular slow

steps. Individual organisms within the population slowly develop the new characteristic. Over time, the entire population shows the successive change toward the new trend.• Ex. The body size of water buffalo will slowly increase to protect

against predators, until the average size of the buffalo is much larger.

Patterns of Evolution• Punctuated Equilibrium: attempts to explain how sudden changes in

species occur. • Ex. This may have happened after the meteor strike that killed the

dinosaurs. The dinosaurs were no longer the dominant organism on Earth, so other organisms began to quickly evolve, more so if the dinosaurs had not been killed.• Another example: Peppered moths of England that quickly evolved

due to the industrial revolution.

Patterns of Evolution• Convergent Evolution: explains how unrelated species can develop

similar characteristics. • Ex. A dolphin and a shark have similar characteristics due to their

environmental demands, like fins and streamlined bodies, but they are unrelated. • These similar structures are called analogous. • Analogous structures are similar in structure and function but have

different ancestors.

Patterns of Evolution• Divergent Evolution: suggest that many species develop from a

common ancestor. This is also called adaptive radiation. • Divergent evolution is demonstrated by homologous structures.• Homologous Structures: body parts that develop from a common

ancestor, thereby having similar structure, but due to subsequent environmental changes, they have different functions.

Patterns of Evolution• Coevolution: occurs when two or more organisms in an ecosystem

evolve in response to each other. This occurs frequently with flowers and their pollinators.• Ex. Orchids have a long tube where their nectar is kept. The

Madagascan Sphinx Moth has a long proboscis to reach the nectar in the orchids tube.

Evidence of Evolution• 1. Anatomical Similarities• Homologous Structures: develop from a common ancestor and are similar in

shape, but have different functions. Ex. The human arm, the wing of a bird, and the flipper of a whale are all homologous structures. They contain the same bones.

Evidence of Evolution• 2. Vestigial Organs: structures that are no longer used or have greatly

decreased in importance. • Ex. A whale and some snakes have a pelvis and femur bones. These

structures are used for walking, but whales and snakes no longer have any use for these structures. The presence of these vestigial organs suggests a common ancestor.

Evidence of Evolution• 3. Molecular Similarities: biochemical similarities demonstrate

relationship among various organisms. DNA sequences are studied and compared. The closer the sequences, the more closely related the organisms.

Evidence of Evolution• 4. Embryonic Developmental Similarities: Closely related organisms

pass through some of the same stages of embryonic development.

Evidence of Evolution• 5. The Fossil Record• A fossil is the recognizable remains or body impressions of an organism that

lived in the past. • Scientists use the fossil record to make hypotheses about the evolution of

organisms.

Evidence of Evolution• Fossils demonstrate changes over time. • Ex. Archaeopteryx is one transitional fossil form that suggests

surviving dinosaurs developed homeothermic mechanisms like feathers or fur. • The fossil record is still somewhat incomplete, but offers evidence

demonstrating how organisms can change.

Extinction• Extinction: occurs when the last living organism of a certain species

dies.• Ex. The Tasmanian Tiger.

Extinction• Ecological Extinction: this happens when a species does not have a

large enough population to sustain genetic diversity. • In this situation, extinction may be a gradual process that happens slowly over

many years.

Ex. Florida Panther has lost most of its habitat and this has reduced the population to a few isolated pockets. Members of this species do not breed easily and often have health problems that stem from inbreeding.

Extinction• Many causes of extinction including, competition for resources,

human interaction with the environment, climate change, loss of food sources, increased predation, disease, and habitat loss.• Modern man has played a role in the extinction of species.• Ex. The passenger pigeon was a common bird in North America. It became

cheap food source for people and the last one died in 1914 in the Cincinnati Zoo.

Extinction• Mass Extinction: this happens when a large proportion of living

organisms on Earth go extinct in a short period of time. • These can be caused by volcanoes, asteroids, or large scale

environmental changes. • The last mass extinction occurred about 65 million years ago and led to

the extinction of the dinosaurs. • During these events, more than 50% of all living things went extinct.

Often, mass extinctions mark the end of geologic eras. • The survivors have many new ecological niches and there is an

explosive amount of diversity.

Extinction• The extinction of the dinosaurs led to the diversity of birds and

mammals. • Some estimate that only 2% of organisms that have ever lived have

survived until today.• Put another way, 98% of all living species that have evolved on Earth

have gone extinct. • Extinction plays an important role in natural selection, because when

a species goes extinct, its niche in the ecosystem is left vacant for other organisms.