Evolution: Exam 1

Biological evolution

The change in heritable characteristics of populations over generations.

Natural selection

The process by which individuals with heritable traits that improve survival or reproduction tend to leave more offspring.

Heritable trait

A characteristic that can be passed from parents to offspring.

Proximate explanation

An explanation of how or what causes a trait or behavior.

Ultimate explanation

An explanation of why a trait exists in terms of evolutionary history.

Application of evolutionary biology

Examples include understanding disease, agriculture, conservation, and other problems involving biological change.

Homologous trait

A similar trait that exists because of shared ancestry.

Analogous trait

A similar trait that evolved independently rather than from shared ancestry.

Whales and evolution

Evidence from fossils, development, and genetics supports the evolution of whales from terrestrial ancestors.

Fossil evidence for whale evolution

The fossil record shows gradual changes as early cetaceans became increasingly adapted to aquatic life.

Developmental evidence for whale evolution

Development can retain ancestral features that provide evidence of evolutionary relationships.

Genetic evidence for whale evolution

Genetic comparisons place whales within the artiodactyl lineage and support their relationship to terrestrial mammals.

O18/O16 and whale fossils

The O18/O16 ratio is higher in saltwater and in bones of animals living in marine environments, so the ratio should increase as whale ancestors became more aquatic.

Hypothetico-deductive method

A method in which scientists propose a hypothesis, make predictions, test those predictions, and use the results to evaluate the hypothesis.

Possible outcomes of a hypothesis test

The hypothesis may be rejected, modified, or provisionally supported.

Hypothesis

A testable and falsifiable proposed explanation.

Fact

A phenomenon or observation that has been repeatedly confirmed.

Scientific theory

A well-supported explanation based on extensive evidence and testing.

Theory vs. hypothesis

A hypothesis is a testable proposed explanation; a scientific theory is a broad explanation supported by extensive evidence.

Darwin's two major hypotheses

Common descent with modification and natural selection as a mechanism of evolutionary change.

Descent with modification

The idea that species descended from common ancestors while accumulating changes over generations.

Common ancestry

The idea that organisms are related through shared ancestors.

Linnaeus

Contributed to taxonomy through hierarchical classification and naming organisms.

Taxonomy

The classification and naming of organisms.

Steno

Contributed to stratigraphy and recognized fossils as remains of once-living organisms.

Stratigraphy

The study of rock layers and their relative positions and ages.

Paleontology

The study of fossils and the history of life.

Cuvier

Provided important evidence for extinction through fossil studies.

Mary Anning

Made important fossil discoveries that contributed to understanding extinct organisms and the history of life.

Buffon

Proposed that species could change over time and considered a much older Earth.

Lamarck

Proposed a comprehensive theory of evolution involving an inherent tendency toward increasing complexity and inheritance of acquired traits.

Inheritance of acquired characteristics

Lamarck's idea that traits acquired through use or disuse during an organism's lifetime could be passed to offspring.

Darwin

Proposed common descent with modification through natural selection and supported his ideas with extensive evidence.

Wallace

Independently proposed natural selection.

Malthus

Argued that populations can grow faster than available resources, creating competition.

Darwin vs. Lamarck

Both proposed that life changes over time; Lamarck proposed use/disuse and inheritance of acquired traits, while Darwin proposed natural selection acting on variation.

Great Chain of Being

The historical idea that organisms exist in a fixed hierarchy from simple to complex.

Why the Great Chain of Being was rejected

Evidence showed that species change and are related through common ancestry rather than forming a fixed hierarchy.

Uniformitarianism

The idea that geological processes operating today also operated in the past.

Why uniformitarianism mattered to Darwin

It helped provide the idea that gradual processes operating over long periods could produce major changes.

Radioactive decay

The natural process in which an unstable atomic nucleus changes into a more stable form.

Radiometric dating

A method of estimating the age of specimens by measuring radioactive isotopes and their decay.

Radiocarbon dating

A type of radiometric dating that measures carbon-14 in biological material.

Why the fossil record is incomplete

Most organisms do not fossilize, and fossilization requires particular conditions.

Age of Earth

About 4.6 billion years old.

Evidence for early life

Evidence comes from fossils, stromatolites, biomarkers, and other geological evidence.

How many times did life originate?

The study guide emphasizes that all currently living organisms share a common ancestor; evidence supports a single lineage leading to current life.

Three domains of life

Bacteria, Archaea, and Eukarya.

Great Oxygenation Event

A major increase in Earth's atmospheric oxygen caused largely by oxygen-producing photosynthesis.

Importance of the Great Oxygenation Event

It changed Earth's environment and allowed aerobic respiration to become important.

Major evolutionary transitions

Major transitions include the evolution of multicellularity and the transition of life onto land.

Multicellularity

The evolution of organisms made up of multiple cells.

Terrestrial life

The evolution of organisms adapted to living on land required traits that helped with challenges such as water loss and obtaining resources.

Major events in human evolutionary history

Early hominid ancestors appeared millions of years ago, followed by later hominid evolution and eventually Homo sapiens.

Phylogeny

The evolutionary history and relationships of organisms or groups.

Phylogenetic tree

A diagram representing a hypothesis about evolutionary relationships.

Branch

A lineage on a phylogenetic tree.

Node

A point where a lineage splits and represents a common ancestor.

Tip/terminal node

A taxon being compared on a phylogenetic tree.

Root

The common ancestor of all taxa shown in a rooted phylogenetic tree.

How to read a phylogeny

Focus on branching relationships and common ancestors, not the left-to-right order of the tips.

Most closely related taxa

Taxa that share the most recent common ancestor.

Clade

A common ancestor and all of its descendants.

Monophyletic

A group containing a common ancestor and all of its descendants.

Paraphyletic

A group containing a common ancestor but excluding some descendants.

Polyphyletic

A group whose members do not include their most recent common ancestor.

Character

A heritable trait used to compare organisms.

Character state

A particular form of a character.

Ancestral character state

A character state inherited from a common ancestor.

Derived character state

A character state that evolved later and differs from the ancestral state.

Outgroup

A related taxon outside the group being studied, used to determine ancestral versus derived character states.

How does an outgroup help?

The character state found in the outgroup can help identify which state is ancestral in the ingroup.

Synapomorphy

A shared derived character that identifies a clade.

Why are synapomorphies important?

They provide evidence for grouping organisms into clades based on shared derived traits.

Parsimony

The principle that the preferred evolutionary explanation requires the fewest evolutionary changes.

How do you choose a tree using parsimony?

Compare possible trees and choose the one requiring the fewest character-state changes.

How do you construct a simple rooted tree?

Use the outgroup to determine ancestral states, compare shared derived characters, group taxa that share derived characters, and choose the tree requiring the fewest changes.

Homology

Similarity of characteristics resulting from shared ancestry.

Homoplasy

Similarity of character states that is not caused by shared ancestry.

Two types of homoplasy

Convergent evolution and evolutionary reversal.

Convergent evolution

When different lineages independently evolve similar traits.

Evolutionary reversal

When a lineage changes from a derived state back toward an ancestral state.

Homology vs. homoplasy

Homology results from shared ancestry; homoplasy does not.

Homologous vs. analogous traits

Homologous traits are similar because of shared ancestry; analogous traits are similar because they evolved independently.

Coelacanths

Lobe-finned fish that share ancestry with tetrapods but are not direct ancestors of modern tetrapods.

Tetrapods

Vertebrates associated with a four-limbed body plan and the transition to terrestrial life.

Lobe-finned fish

Fish closely related to tetrapods that provide evidence about the transition from aquatic to terrestrial vertebrates.

Tiktaalik

A transitional fossil with both fish-like and tetrapod-like characteristics.

Why is Tiktaalik important?

It provides evidence about the evolutionary transition from aquatic vertebrates to tetrapods.

How was Tiktaalik found?

Neil Shubin used evolutionary and geological predictions to identify rocks and locations likely to contain transitional fossils.

Acanthostega

An early tetrapod that helped show that limbs evolved before tetrapods were fully adapted to life on land.

Tetrapod limbs as exaptations

Limbs may have originally served functions in aquatic environments and were later used for movement on land.

Archaeopteryx

A fossil with both dinosaur-like and bird-like characteristics.

Evidence that birds evolved from dinosaurs

Fossils such as Archaeopteryx and shared characteristics support the evolutionary relationship between birds and theropod dinosaurs.

Theropods

A group of dinosaurs from which birds evolved.

Exaptation

A trait that evolved for one function and was later co-opted for another function.

Feathers as an exaptation

Feathers evolved before flight and were later used for flight.

Early ideas about inheritance

Ideas such as blending inheritance and inheritance of acquired characteristics attempted to explain heredity but could not adequately explain how variation was maintained.

Blending inheritance

The incorrect idea that parental traits blend together in offspring.

Particulate inheritance

The idea that hereditary factors are discrete rather than blending together.