Evidence for Evolution and Geological Eras

Evidence for Evolution

• Paleontology
  • The first evidence for evolution was observed in fossils.
  • New organisms were discovered in the fossil record.
  • Most of these organisms are now extinct.
  • Geological time scales went through several hypotheses until radioactive dating was discovered.
  • The Earth is 4.6 billion years old.

Geological Eras

• Time periods are marked by mass extinction events.
  • 65 million years ago, non-avian dinosaurs went extinct. Birds are closely related to dinosaurs.
  • 248 million years ago, nearly all life went extinct.
  • Between 90-97% of life went extinct.

Fossils

• Fossils form through various methods, but all are rare processes.
  • Compression: Sediment settles above and below a dead organism, resulting in remains.
  • Petrifaction: Hard body parts are replaced by minerals in the soil.
  • Imprints: Outlines of the organism are left behind.

How Old are Fossils?

• Relative dating: Lower layers of the Earth are generally older than higher layers. This doesn't give an actual date but provides chronological information.
• Absolute dating: Based on radiometric dating.

Radiometric Dating

• Radiometric dating provides an actual time period.
  • Errors in experiments must be accounted for within the observed time range.
  • Radioactive isotopes change structure in a set pattern over time.
  • Carbon-14 is good for up to 40,000 years.
  • Potassium-Argon is suitable for 100 million to billion-year ranges.

Missing Links

• In Darwin's Origin of Species, he discussed challenges related to the lack of transitional fossils.
• Transitional fossils have been discovered since then showcasing intermediate forms.

Biogeography

• This is the study of a species' geographical distribution.
• The theory of plate tectonics describes the mechanism of the Earth's surface motions.
  • Helps describe earthquakes.
• Helps explain the distribution of the fossil record.

Island Biogeography

• Islands have a unique form of biogeography.
• Reptiles, arthropods (insects, spiders), and birds are commonly successful colonizers of islands.
• Reptiles are often larger while birds sometimes lose the ability to fly on islands.
• Mammals and amphibians have difficulty colonizing islands.
• Mammals often become smaller on islands as there are often no new ecological niches available.
• Island species develop through adaptive radiation.

Anatomical Structures

• Biological evolution produces similar anatomical patterns in closely related organisms.
• Homologous, vestigial, and analogous structures are studied.
  • Homologous structures share a common evolutionary origin, similar genetic development, and embryonic development.
  • Vestigial structures were once functional but lost their use over time.
  • Analogous structures have similar functions but different evolutionary origins.

Homology of Genetics

• The PAX6 gene produces a transcription factor.
• This factor controls how other genes are transcribed and is essential for eye development in many bilaterian animals.
• Homologies exist across diverse species like arthropods, mollusks, and vertebrates.

Vestigial Structures

• Vestigial structures are organs which lost their original function.
• Pilo erector muscles on mammals once served for warmth and creating a larger appearance.
• Many whales and snakes still possess vestigial pelvic structures from their tetrapod ancestors.

Whale Pelvic Structures

• Whales evolved from terrestrial tetrapods.
• Their genetic makeup still includes pelvic structures.
• They lack a fully developed tail.

Analogous Structures

• Structures that appear similar but have different evolutionary origins often have the same function.
• Example: Wings of birds and insects.
• Convergent evolution explains how similar structures evolve in unrelated organisms.

Marsupials and Placental Mammals

• Mammals have three main groups: placentals, marsupials, and monotremes.
• Marsupials were dominant in Gondwana, while placentals were dominant in Laurasia.
• North American and South American landmasses have placental mammals.

Embryonic Development

• Evolutionary relationships can be studied using embryonic development.
• Organisms with a closer evolutionary relationship often show similar embryonic stages.
• Homeotic genes control development in organisms.

Ernst Haeckel

• 19th-century German naturalist.
• Studied comparative embryology.
• Sometimes exaggerated data to illustrate his points.

Comparative Molecular Biology

• Evolution can be traced by comparing DNA, RNA, and proteins in organisms.
• Organisms with similar patterns in their DNA, RNA, and proteins are more closely related.
• Not just functional genes, but also pseudogenes and transposons are also used to analyze evolutionary relationships.

Case of the Missing Chromosome

• Humans and chimpanzees are closely related despite having a different number of chromosome pairs.
• Chromosome 2 in the human genome has two centromeres and a telomere, similar to a fused chromosome.

Human vs. Chimpanzee Karyotype

• Two chromosomes in chimpanzees are fused into one in humans.
• The genes are the same in the equivalent chromosomes.
• All other apes have these chromosomes in their genome.

Vitamin C

• Most mammals have a gene for producing vitamin C.
• Humans lost the functionality of this gene.
• This loss occurred in the common ancestor of apes.

Evolutionary Tree of the Great Apes

• Mutations in a common ancestor led to the evolution of different ape species.

Molecular Clock

• Molecular clocks estimate the time of divergence in organisms.
• The assumption is made that rates of mutations are consistent among organisms.

Darwin's Finches

• Finches in the Galapagos Islands show adaptive radiation.
• Various beak structures result from environmental pressures.

Explore the fascinating evidence for evolution as captured through paleontology and fossils. Understand the significance of geological eras marked by mass extinction events and how fossils are formed and dated. This quiz delves into key concepts that illustrate the history of life on Earth.