Evolution Mechanisms Quiz

Evidence for Evolution

• Evolution: a change in the overall characteristics of a group of organisms (populations) over multiple generations. Populations evolve, not individuals.

• Population: a group of individuals of the same species living in a defined area.

Mechanisms of Evolution

• Natural selection: a process by which individuals with advantageous inherited characteristics for a particular environment survive and reproduce at a higher rate than those with less useful characteristics. Those that survive longer to reproduce will pass on their traits, and the traits that help survival will become more common in the population.

• Genetic drift: the frequency of a neutral mutation (no positive or negative effects) randomly increases in a population.

Evolution by Natural Selection

• Survival of the fittest: Individuals that survive long enough to reproduce will pass on their advantageous traits. The individuals with the most offspring are the most successful.

Natural Selection Examples

• Birds with larger beaks: During times of drought, only large, tough seeds are available. Birds with larger beaks are more successful at eating these seeds, increasing their survival rate. Their offspring will also have larger beaks. Smaller beaks are less successful.

Evidence for Evolution

• Direct observation through artificial selection: artificial selection that changes organisms. For example: selective breeding of dogs to get desired traits.
• Fossil evidence: mineralized remains or impressions of formerly living organisms. Fossils can show how common ancestors evolved over time.
• Shared characteristics among living organisms: organisms that share traits or have similar body parts likely share a common ancestor. They developed similar traits, and descended from this ancestor.
• Similarities and differences in DNA: Similar DNA sequences indicate common ancestry. Pseudogenes are non-functional genes but they are related to similar genes in other organisms, which is evidence of ancestry.
• Biogeographic evidence: the geographic locations where fossils or organisms are found. Related organisms often exist in regions with similar environments or that were close together in the past.
• Common patterns of embryo development: similarities in early development, with gill slits and tails in vertebrates, suggest common ancestry.

Artificial Selection

• Artificial selection: biological evolution for desired traits caused by humans performing selective breeding. It's an intentional change brought about by selective reproduction.

Fossils

• Fossils: the mineralized remains or impressions of formerly living organisms.
• They show how living organisms have changed over time. Fossilized remains are also used to determine the age of the earth's rocks and layers.
• Fossil record: Enables biologists to reconstruct the history of life on Earth. Transitional fossils show evidence of species with traits that show similarities to an ancestor and to descendant species. These "in-betweens" help us better understand the evolution over time.

Whale Ancestors

• Whale ancestors: Evolved from a land-dwelling mammal to a water-dwelling mammal. This is supported by the evolution of their skeletal structures, oxygen isotopes in their teeth, and similar traits among land and water-dwelling mammals.

Adaptive Traits

• Adaptive trait/adaptation: a feature that gives an individual improved function in a competitive environment.
• Modern animals that live in shallow water likely have thick bones to prevent floating and help with diving quickly.

Adaptations take many forms

• Example: Echolocation in bats for finding insects in the dark, and stick insects mimicking plants to avoid detection.

Recap

• Adaptations: Features enabling organisms to function well in the specific environment they live in.
• Vestigial traits: Are inherited from ancestors but are no longer useful.

Shared Characteristics among Living Organisms

• Shared characteristics: Many shared characteristics are a result of a common ancestor.
• Common ancestor: The original organism from which many species have evolved.
• Common descent: The sharing of a common ancestor by two or more different species.

Shared Characteristics of Mammals

• All mammals: share similar characteristics like hair or fur, breathing air, mammary glands, giving birth to live young, and maintaining a constant internal body temperature.

Homologous Traits

• Homologous traits: similar structures in organisms of common descent. Inherited from a common ancestor. These traits often appear different in their current use and structure.
• Example: Humans, whales, and bats all have five-fingered or equivalent limb structure.

Recap

• Common ancestor: a shared species from which the species evolved.
• Homologous traits: traits with the same origins but may have different functions.
• Commonalities of organisms: similar skeletal structures, DNA, egg-laying, oxygen acquisition strategies and others.

Vestigial Traits

• Vestigial traits: another type of trait that many related organisms have that is inherited from a common ancestor, but is no longer useful.
• Example: Reduced hind legs in snakes, or goose bumps in humans.

Recap

• Vestigial traits: inherited from a common ancestor, but are no longer useful.

Similarities and Differences in DNA

• DNA: all living organisms on Earth use DNA as hereditary material.
• Genetic code: the universality of the genetic code, similar DNA sequences, is one of the strongest indicators that all living things evolved from a common ancestor.

Pseudogenes

• Pseudogenes: are genes that code for proteins, but are now non-functional or inactive.

Recap

• DNA sequence similarities of related organisms point to common ancestry.

Biogeography

• Biogeography: Study of geographic distribution of organisms.
• Location of fossils: Geographic locations where fossils are or should be found (biogeography) relates to evolutionary patterns.
• Example: Evolution of whales from land to water - early whale fossils found in river and lake areas, and later whale fossils are in ocean areas, which supports the evolutionary pathway.

Recap

• Biogeographic evidence shows that organisms related geographically.

Embryonic Development

• Embryonic development: how an organism develops from a zygote. Related species share similarities in early development stages.
• Example: Gill slits and tails in vertebrate embryos. These similarities suggest a common ancestor.

Recap

• Similarities in embryonic development suggest a common ancestral origin.

Review

• Common ancestor: Animals that share genes and proteins for the same functions that indicate organisms descended from a common ancestor.

Review

• Natural selection evidence: Natural selection evidence includes similarities in embryonic development, and similar traits that have changed in organisms. However, the diversity of domestic dogs is not evidence of evolution by natural selection.

Review

• Homologous traits: traits that are no longer useful in a specific organism are known as vestigial traits.