Evolution

Biogenesis

Abiogenesis

Before the 1600s, it was generally thought that organisms could arise from nonliving material by spontaneous generation

Francesco Redi

Redi showed in 1668 that rotting meat kept away from flies would not produce new flies

Maggots appeared only on meat that had been exposed to flies

Lazzaro Spallanzani

Spallanzani showed in the 1700s that microorganisms would not grow in broth when its container was heated and then sealed

This seemed to indicate that microorganisms that cause food spoilage do not arise from spontaneous generation but, rather, are carried in the air

Louis Pasteur

Pasteur used a variation of Spallanzani’s design to prove that microorganisms are carried in the air and do not arise by spontaneous generation

Fossil Record

Fossils

A fossil is a trace of a long-dead organism

The law of superposition states that new geologic strata are deposited on top of older strata

The history of Earth and its life-forms can be inferred by examining the fossil record

Fossil Record

The fossil record shows that new life-forms have arisen continually during the history of life on Earth

Biogeography

The study of biogeography shows that organisms arise in areas where similar, now-extinct organisms once lived

Theories of Evolution

Jean Baptiste de Lamarck

Lamarck proposed that species evolve over time

He incorrectly hypothesized that species modification is the result of acquired characteristics and that these characteristics can be passed on to offspring

Charles Darwin began his work on evolution when he was employed as a naturalist for a voyage of the H.M.S. Beagle

Uniformitarianism

Darwin was influenced by Charles Lyell, who proposed the principles of uniformitarianism, which hold that the structure of Earth results from cycles of observable processes

Adaptive Radiation

Darwin found evidence of species modification in both modern and extinct species

Darwin hypothesized that related species, such as the Galapagos finches, descended from a common ancestor

Natural Selection

Darwin wrote The Origin of Species, in which he proposed that natural selection is the principal driving force behind evolution

Adaptation

A population of organisms adapt to their environment as their proportion of genes for favorable traits increases

So what exactly is evolution?

Evolution is the change in genetic makeup of a population over generations

HOMEWORK!!!

Can you create the perfect habitat for each of these wild canines?

Using magazine clippings, crayons, and markers, illustrate a habitat you think each canine is well suited for.

Life in the Grasslands…

The maned wolf is well adapted for life in the tall grass plains or pampas of South America. Their stilt-like legs aren't for running -- this canine is no speedster. Instead, long legs help maned wolves peer over tall grasses to spot each other and their prey.

Life in the Desert…The fennec fox makes its home in the desert. Pale fur reflects the sun's rays, and extends over the soles of its paws to protect against burning desert sands. When fennec foxes overheat, they shunt or send blood to their large ears to rapidly dump the excess body heat into the environment.

Life in the Arctic…

Not many wild canines can survive the frigid temperatures of the arctic. The arctic fox is the only year-round small canine resident of this harsh environment. Its fur goes from white in winter to brown-gray in summer, keeping in line with the seasonal change from white snow cover to brown tundra. To keep warm, it has thick fur that even covers the soles of its feet and tiny ears to reduce heat loss when the temperature dips far below zero.

Life in the Forest…

The gray fox has a unique adaptation for life in the forest. In addition to small body size and short legs that make it easy to move through the underbrush, the gray fox is the only climbing canine. Using its somewhat curved claws, it scampers up trees to avoid predators as well as to forage for food such birds or their eggs.

Evolution in Process

Body Structures

Evidence supporting evolution is found in the body structures of living organisms

Homologous structures have a common structure

Analogous structures are similar in function but have different structure

A species with vestigial structures probably shares evolutionary origins with a species that has a functional forms of the structure

Homologous Structures

Analogous Structures

                                                                                                       

                                                       

Vestigial Structures

Embryological & Molecular Evolution

Similar embryological development among species indicates a common evolutionary history

Similarity in macromolecules such as RNA, DNA, and proteins indicates a common evolutionary history

Coevolution

In coevolution, two or more closely associated species, such as a predator and its prey, change in response to each other

Convergent Evolution

In convergent evolution, organisms that are not closely related resemble each other because they have responded to similar environments

Divergent Evolution

In divergent evolution, related populations become less similar as they respond to different environments

Adaptive radiation is a type of divergent evolution

Disruption of Genetic Equilibrium

Genetic Equilibrium Shifts

Evolution can take place if the genetic equilibrium of a population is disrupted Immigration Nonrandom mating Genetic drift Stabilizing selection Directional selection Disruptive selection Sexual selection

Immigration & Emigration

Immigration can bring new genes into a population, causing evolution

Emigration is the movement of individuals out of a population

Nonrandom Mating

Nonrandom mating can alter the genotypes of a population, but does not affect allele frequencies

Genetic Drift

Genetic drift operates in small populations; the contribution or lack of contribution of the genes of one or a few organisms can change the population’s gene pool significantly

Stabilizing Selection

Stabilizing selection encourages the formation of average traits

Directional Selection

Directional selection encourages the formation of more-extreme traits, such as a very long tongue in anteaters

Disruptive Selection

Disruptive selection selects for extreme traits rather than average traits

Sexual Selection

In sexual selection, the development of traits that may seem harmful can actually enhance reproductive fitness if they encourage mating

Formation of Species

Species Definition

According to the biological species concept, a species is a population of organisms that can successfully interbreed and cannot breed with other groups

Speciation

Speciation means species formation, and it always begins with a population that has become isolated

Geographic Isolation

Geographic isolation results from the division of an original population

Reproductive Isolation

Reproductive isolation results from barriers to successful breeding

Prezygotic isolation occurs before fertilization

Postzygotic isolation occurs after fertilization and results in wasted gametes