Evolution: Chapter 11 Evidence

• Evidence for Evolution is covered in Chapter 11
• Copyright 2024 W. W. Norton & Company, Inc.

Objectives

• Evolution needs to be defined, and six lines of evidence listed
• Artificial and natural selection should be contrasted
• The fossil record supports evolution
• Homologous and vestigial traits support common descent
• Distantly related species exhibit similar DNA
• Knowledge of evolution and continental drift help predict locations of fossils
• Similarities in embryonic development reveal shared evolutionary past

Evolution

• Evolution changes the inherited characteristics of a group of organisms across generations
• Evolution explains the way living things look and act
• Populations is what evolves, not individuals

Six Lines of Evidence for Evolution

• Observing evolution through artificial selection
• Fossil evidence
• Shared characteristics among life
• Similarities and Difference in DNA
• Biogeographic evidence
• Comparing common patterns in embryo development

Domestication: Artificial Selection

• Domestication involves taming animals or cultivating plants for human benefits
• All dogs belong to one species Canis lupus familiaris, a gray wolf subtype
• Domestication of gray wolves began 16,000 years ago
• Humans bred wolves to get desired traits

Natural vs. Artificial Selection

• Artificial selection results from selective breeding
• Selective breeding involves humans only allowing individuals with desired inherited traits to mate
• Humans choose certain individuals to reproduce particular traits over others

Natural Selection

• Nature or the environment decides which variations survive and reproduce
• Most successful breeding have characteristics that are more common in future generations

Adaptation

• Populations experiencing natural selection evolve so more and more individuals have beneficial traits
• Fewer individuals have disadvantageous traits as a result
• Adaptation: populations better match their environment over time because of evolution

Adaptive Trait

• It gives an individual a better function than competitors
• Echolocation is an adaptation that helps bats catch insects in the dark
• Mimicking plants helps stick insects avoid predators

Finch Adaptation

• During drought, finches need large, hard seeds
• During rainy times, small seeds are more common
• If the environment supports both beak types, both remain in the population

Fossils

• Fossils are a mineralized remain or impression of a formerly living organism

Fossils and Ancient Geography

• Reveals the age of the rocks
• Fossilized organisms reveal the environment at the time
• This indicates how organisms functioned
• Earth movements (mountain buildings) are a component of ancient geography
• Evolution of life on Earth can be discovered

Fossils And Time

• Provides strongest evidence of evolution
• The depth or distance from the surface where a fossil is in relation to Earth indicates its timeline
• Older fossils are in deeper rock layers

Transitional Fossils

• Displays similarities to both ancestral and descendant groups
• The wolflike Pakicetus waded in shallow freshwater and is the oldest whale ancestor
• Next came the crocodile-like Ambulocetus, which stalked prey underwater
• Next came the fully aquatic Dorudon, which had a blowhole, flippers, and a tail
• Thewissen searched for the ancestor that lived on land

Whale Fossils

• Indohyus was likely a whale relative that lived near water and spent lots of time there
• The oxygen isotope levels in teeth matched water-going mammals today
• The crushing molars suggest it grazed on plants
• Modern animals in shallow water have thick bones

Fossil Fuels

• Aquatic plants and animals die and are buried on the ocean floor by layers of sand and silt for 300-400 million years
• Layers of sediment are deposited above and the pressure and heat causes compaction for 50-100 million years
• The remains become oil and gas, which are forced out of porous rock

Shared Characteristics of Living Organisms

• Shared characteristics result from a common ancestor
• Common ancestor: a single organism that many species evolved from
• Common descent occurs when a group of organisms share a common ancestor

Forebones

• Chicken wings are forelimbs exhibiting homologous structures

Homologous Traits

• Existing structures are easily modified compared to evolving new ones
• Homology involves anatomical, genetic, or developmental similarity among organisms due to common ancestry
• They look different over time

Vestigial Traits

• Features inherited from a common ancestor but are no longer used
• The traits may appear as reduced or degenerated parts

DNA Similarities And Differences

• All life uses DNA, which is deciphered using the same code
• This includes organisms as different as bacteria, redwood trees, and humans
• The common genetic code is evidence supporting evolution from a common ancestor

DNA Sequence Similarity

• DNA sequence similarity is a measure of how closely related two DNA molecules are to each other

Biogeography

• The continents are on tectonic plates that move slowly
• Continental drift or plate tectonics refers to the movement
• ~250 million YMA, all landmasses had drifted together to form Pangaea
• ~200 million YMA, Pangaea split up to form the continents as we know them today
• Today the separation continues
• Biogeography of a species: geographic locations of where fossils can be located

Embryo Development

• It's how an embryo grows and develops
• It mirrors developmental stages of ancestors
• Shared patterns descend from a common ancestor

Embryo Development PT 2

• Embryos of fish, reptiles, birds, and humans all share gill slits and tails
• This is because all those species evolved from a common ancestor with these features