Evolution Chapters 14 and 15

Earth’s Origin (pg.279)

• The Earth was formed approximately 4.6 billion years ago (bya)

• Gas and dust formed into a sphere and cooled - solid rocks formed 4 bya.

• Several ideas have emerged:• Biogenesis -

• Life comes from life, but how did the first life begin?

• Abiogenesis -• Spontaneous Generation:

the idea that living things can arise from non-living.

• Creationism -• “A God or Gods” created life

It is thought that a combination of gases and lightning could have possibly formed organic molecules that produced living cells; this has never really been duplicated.

Chapter 14 - History of Evolution

Earths History (pg.282) - Estimated age of Earth is > 4 billion yrs. (byr) - Scientist have studied the earths geology and have a pretty good idea of hist history.

Radiometric Dating (pg. 282-284)

- This uses isotopes (elements with different number of neutrons. ex. carbon 12 and 14) - Some isotopes have unstable nuclei which undergo radioactive decay - nuclei radiate energy until they become stable. -Half Life - length of time it takes for on-half of an isotope to decay to a stable form.

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The First Life Forms (pg. 287-288)

- RNA plays a vital role in DNA replication and protein synthesis. - The chemistry and genetics of early life was based on RNA. - Theory is self-replicating RNA started to evolve inside cell-like

structures.- The self-replicating RNA could have provided the hereditaryinformation that the cell-like structures lack. - Ribozyme - RNA molecule that can act like a catalyst and promote a chemical reaction. - If RNA molecules could direct the assembly of the structures that carried them, a cell-like system could be formed.

The First Cells - Scientist make inferences:

-First cells might have developed in an environment filled with organiccompounds (carbon compounds) for food. - Thus first cells were probably Anaerobic (without oxygen), heterotrophic (rely on others for food) and prokaryotes (single cell and lack a nucleus).

The first life to form were prokaryotic, anaerobic, and ???______trophs.

It is uncertain how living cells were first created.

- Autotrophs (self -feeders) most likely did not depend on the sun for energy like photosynthetic autotrophs but instead relied on chemosynthesis.

- Archaea: area group of single-celled organisms that thrive in harsh conditions.

- They live in anaerobic environments and obtain energy by the process of chemosynthesis (Energy is obtained from the oxidation of various inorganic substances such as sulfur)

Photosynthesis and Aerobic Respiration (pg. 289):

- chemical traces of photosynthesis (using suns energy to make food) dates back to 3 billion yr.

- Fossils indicate organisms similar to todays cyanobacteria a group of photosynthetic single-celled organisms.

Photosynthesis and Aerobic Respiration (pg. 289):

- Oxygen (O2) a by-product of photosynthesis was damaging to early unicellular organisms.

- Within some organisms, oxygen bonded to other compounds preventing damage.

- This bonding was the first steps in aerobic respiration (with oxygen).

- It took billions of years for the oxygen to reach the levels we have today.

- the oxygen moved to the upper atmosphere where in the present of sunlight reacted and ozone (O3) was formed.

- Ozone is poisonous to both plants and animals but in the upper atmosphere, a layer of ozone absorbs ultraviolet radiation which can damage DNA.

The First Eukaryotes (pg. 290):

- Eukaryotic cells differ from prokaryotic cells.

- Eukaryotic cells are larger, DNA is organized into chromosomes in a nucleus and they have membrane bound organelles. These features are thought to have EVOLVED from prokaryotic cells.

- The thought is that primitive Eukaryotic cells engulfed aerobic prokaryotic cells and these evolved into todays mitochondria, which perform cell respiration (aerobic). The organelle that is responsible for breaking down sugars to make ATP (intracellular energy).

- Engulfed photosynthetic cyanobacteria became todays chloroplasts. The organelle responsible for photosynthesis.

- Evidence supports this theory, both mitochondria and chloroplast have their own genetic material and they replicate independently of the cell.

• The idea that life has changed over time. Modern organisms descended from ancient organisms.

Chapter 15 - Theory of EvolutionEvolution - Defined

Early Evolutionary Thoughts (pg 297-299)

• Proposed by Jean Baptiste de Lamarck (1809)

• Assumed three things:

• Thought that organisms have an inborn desire to change to become more fit. example: Birds want to fly from predators.

• “Use and Disuse” - unused parts would disappear, used parts could change.

• “Passing on Acquired Traits” ex: Doberman’s clipped ears would be passed to puppies.???

• Lamarck’s “theory” could not be supported with actual data.

• He paved the way though for Darwin’s Theory of Evolution.

Charles Darwin (pg. 299)

• 1831 - Set sail on the HMS Beagle

• Darwin was amazed by the diversity of life on earth

• 99.9% of all organisms that once lived on earth are extinct

• He recognized that the goal of evolution is to make an organism ‘fit’ into the environment in a successful way

Survival of the Fittest / Natural Selection (pg. 300-301)

• Individuals whose characteristics are well-suited to their environment survive. Individuals whose characteristics are not well suited either die or leave few offspring

• Example - Peppered Moth• Fitness (traits and behaviors that allow an organism to survive and

reproduce) occurs through adaptation• Example - Animals with thick fur would survive the cold

• TIME is the key• Natural Selection occurs over a much longer time than artificial

selection.

Reproduction Isolation

• Isolation is an important factor in species formation. It allows differences to develop.

• Species can be linked based on similar structures that changed over time.

Natural Selection -Darwin proposed the mechanism for descent with modification.

• Darwin came up with the theory that could have caused changes in organisms over time.

• Overproduction - more offspring can be produced than can survive to maturity. Darwin realized that the environment limits the populations of all organism by causing deaths, limiting populations.

• Genetic Variation - within a population, individuals have different traits. Occasionally new traits appear in a population (due to mutation)

• Struggle to Survive - individuals must compete with each other in what Darwin called “ struggle for existence”. Some variations improve an individuals chance of survival and reproduction. Some variations will reduce the chances. A trait that makes an individual successful is called an “ADAPTATION”

• Differential Reproduction - animals with the best adaptations are most likely to survive and reproduce and thus get their genetic information out there. The adaptation will become more frequent in the population.

Darwin Suggests Natural Selection Could Account for Descent with Modification.(pg. 302)

• As species became better adapted to different environments.

• That is the “Theory of Natural Selection” proposes that nature changes species by selecting traits.

• Survival of the Fittest describes the idea of Natural Selection.

• In evolutionary terms, “Fittest” is a measurement of an individuals hereditary contribution to the next generation.

Evidence for Evolution (pg. 302)

• Fossil record: A fossil is the preserved remains of ancient organisms and the relative age is determined by the layers of earth

• DNA similarities: Two organisms are closely related if they have similar DNA

• Embryology: Similarities in embryonic development reveals kinship

• Immunological Testing: Similarities in blood constituents.

• Homologous/Analogous Structures

The Fossil Record (pg. 302-304)

• Superposition - states that the rock strata if not disturbed will have the lowest strata formed before the one above.

• 1700s -1800s geologists began to put together a timeline fro the order in which different groups of rocks and fossils were formed. (geologic time scale).

• Relative Age - age compared to that of other fossils by referring to the geologic timescale.

• Absolute Age -determined by radioactive dating.

Radioactive Dating

•This is determining the age of something by the decay of its radioactive elements

•Example - Carbon 14

Distribution of Fossils

• Different fossils lived at different times.

• Todays organisms are different from those of the past.

• Fossils found in adjacent layers are more like each other than then to fossils found deeper.

• Example - different species of trilobites appear in nearby strata, where deeper and older strata do not have trilobites.

Transitional Species (pg. 304)

• Transitional Species - species have differed in a gradual sequence of forms over time.

• Transitional species have features that are intermediate between those of hypothesized ancestors and later descendant species.

• Modern marine mammals like whales evolved from early mammals in the fossil record that once walked on land.

• Fossils have been found to support this, these are the transitional forms.

Biogeography (pg. 305)• Biogeography is the study of the location of

organisms around the world.

• Charles Darwin and Alfred Wallace saw evidence of evolution in the distribution of organisms.

• Both observed animals that seemed closely related yet adapted to different environments.

• Also they observed animals that seemed unrelated but had similar adaptations to similar environments.

• Example - mammals of Australia provide evidence. Native Australian animals resemble wolves, cats, mice and more. However, most are marsupials, which could have evolved in isolation on the Australian continent.

Anatomy and Embryology (pg. 305)

• Descent with modification also predicts the findings of anatomy - the study of body structure of organisms.

• Embryology - the study of how organisms develop.

Homologous Structures(pg. 305)

Structures that develop from the same body part. Anatomical structures that occur in different species and that originated by heredity from a structure in the most recent common ancestor.

Niches

• Species are found in niches = their job and location

• No two species can occupy the same niche- they will compete and the fittest will “win.”

• Allows for the development of analogous structures

• Analogous Structures are similar in appearance and function, but have different origins unlike homologous

Analogous Structures(pg. 305)

These are structures that have closely related functions but do not derive from the same ancestral structure.

Even though birds, bats, and moths have wings, have wings, their wings have very different underlying structures.

Biological Molecules (pg. 306)

Modern studies of biological molecules support the prediction that organisms that share many traits have a common ancestor.

Biologist can compare the DNA, RNA, and proteins from many different organisms and look for similarities and differences.

The greater number of similarities between any given species, the more closely the species are related.

Developing Theory (pg. 306-307)

Modern Synthesis of Evolution - 1900s Scientists integrated the Theory of natural selection with the understanding of genetics.

Some aspects of evolution remain a unknown. However it is widely accepted.

Phylogeny - the model of the relationship by ancestry among groups of organisms.

More closely related groups appear closer to each other on a branch.

Evolution in Action (pg. 308-309)

Convergent Evolution - the process by which different species evolve different traits. Different species come from different ancestors but evolve similar traits through adaptation to a similar environment.

Divergent Evolution - process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment.

Adaptive Radiation - when a new population in a new environment such as an island will undergo divergent evolution until the population fills many parts of the environment.

Artificial Selection (pg. 310)

• The intervention of humans ensures that only individuals with desirable traits produce offspring

• Darwin also talked to farmers and found that they use natural variation to their advantage by choosing organisms that would best benefit them

• Darwin realized that there was a natural process that operates in a way similar to artificial selection

Coevolution( pg. 310)

When two or more species have evolved adaptations to each other’s influence.

Mimicry is a similarity of one species to another which protects one or both.This similarity can be in appearance, behavior, sound, scent or location. Mimics are found in the same areas as their models.

Microevolution

Evolution at the genetic level. Thisis a change in the collective genetic material of a population.

Within a population, individuals may vary in observable traits.

Example: Peppered Moth

The End