Botany 130 Unit 3 - Lecture

Common descent

The idea that all organisms descended from shared ancestors.

Special creation

Hypothesis that each species was independently created in its current form.

Extinction

The permanent disappearance of a species.

Mutability

The ability of species to change over time.

Descent with modification

The process by which species evolve from common ancestors and accumulate changes over generations.

Biogeography

The study of the geographic distribution of organisms.

Vestigial trait

An inherited structure that has lost most or all of its original function.

Homology

Similarity between structures due to inheritance from a common ancestor.

Homologous structures

Structures that are similar because they were inherited from a common ancestor.

Universal common ancestor

The ancestral population from which all life on Earth descended.

Common ancestor

An ancestral organism shared by two or more evolutionary lineages.

Phylogenetics

The study of evolutionary relationships among organisms, genes, or populations.

Phylogeny

The evolutionary history and relationships of organisms, genes, or populations.

Lineage

An evolutionary line of descent connecting ancestors to descendants.

Phylogenetic tree

A branching diagram representing evolutionary relationships among organisms or other lineages.

Phylogenetic hypothesis

A proposed explanation of the evolutionary relationships among organisms.

DNA sequence

The specific order of nucleotide bases in a DNA molecule.

DNA substitution

A change in a nucleotide base at a particular position in a DNA sequence.

Nucleotide

A building block of DNA consisting of a sugar, phosphate, and nitrogenous base.

Probability

A measure of how likely an event or outcome is to occur.

Likelihood

A measure of how well a particular hypothesis explains observed data.

Statistical model

A mathematical representation used to analyze data and evaluate hypotheses.

Inductive reasoning

Reasoning that uses specific observations to develop broader conclusions.

Conserved protein

A protein that has remained similar throughout evolution because of its important function.

Genetic code

The set of rules that determines how nucleotide sequences are translated into proteins.

Endemic species

A species naturally found only in a particular geographic location.

Ancestral species

An earlier species from which later species evolved.

Evolutionary relationship

A connection between organisms based on their shared ancestry.

What is common descent?

The idea that all organisms evolved from shared ancestors.

What is descent with modification?

Species inherit traits from ancestors but accumulate changes over generations.

What are the three major lines of evidence for descent with modification?

Biogeography, vestigial traits, and homology.

Why is extinction inconsistent with special creation?

Fossils reveal organisms that existed in the past but no longer exist today.

What evidence from fossils supports evolution?

Fossils show that organisms from the past were different from organisms living today.

Why is the mutability of species inconsistent with special creation?

Species change over time rather than remaining permanently unchanged.

How does biogeography support common descent?

Species in nearby geographic regions often resemble one another because they descended from nearby ancestral populations.

Why do many Galapagos species resemble South American species?

They likely descended from ancestors that reached the Galapagos from South America.

What is an endemic species? Delete

A species naturally restricted to a specific geographic region.

How do vestigial traits support evolution?

They show that organisms inherited structures from ancestors even when those structures are no longer needed.

What is an example of a vestigial plant trait?

Cactus leaves have been modified into spines, reducing water loss.

How do homologous structures support evolution?

They show that organisms inherited similar structures from a common ancestor and modified them over time.

Why are onion bulbs evidence of homology?

They contain nodes, leaves, and buds, showing that they are modified stems.

What is the universal common ancestor?

The ancestral population from which all living organisms descended.

What characteristics do all known living organisms share?

They use amino acids to make proteins, use DNA with a very similar genetic code, and share conserved proteins.

Why is a universal common ancestor a strong explanation for similarities among organisms?

Shared molecular characteristics are much more likely if organisms inherited them from a common ancestor.

What is the difference between special creation and common descent?

Special creation proposes that species originated independently while common descent proposes that species evolved from shared ancestors.

Why is common descent a better explanation for biological diversity?

It explains similarities, differences, extinction, and changes in organisms through shared ancestry and evolution.

What is phylogenetics?

The study of evolutionary relationships among species, populations, and genes.

What is the difference between phylogenetics and phylogeny?

Phylogenetics is the study of evolutionary relationships while a phylogeny is the evolutionary history or representation of those relationships.

What does a phylogenetic tree represent?

Hypothesized evolutionary relationships and common ancestry.

Why are phylogenies important?

They help scientists understand biodiversity and form and test evolutionary hypotheses.

How do scientists infer evolutionary relationships using DNA?

They compare DNA sequences and use statistical models to determine which evolutionary relationships best explain the observed similarities and differences.

Why is DNA useful for determining evolutionary relationships?

It provides large amounts of measurable genetic information that can be compared across organisms.

What are the main steps of phylogenetic inference using DNA?

Develop possible phylogenetic hypotheses, calculate DNA substitution probabilities, and calculate the likelihood of each hypothesis.

What happens during the first step of DNA based phylogenetic inference?

Scientists develop possible evolutionary trees that could explain the relationships among organisms.

What happens during the second step of DNA based phylogenetic inference?

Scientists calculate the probabilities of different numbers of DNA substitutions.

What happens during the third step of DNA based phylogenetic inference?

Scientists calculate the likelihood of each evolutionary hypothesis using the DNA data.

How does branch length affect DNA substitution probabilities?

Longer branches generally allow more time for substitutions and have a higher probability of multiple changes.

What does likelihood measure in phylogenetic inference?

How well an evolutionary hypothesis explains the observed DNA sequence data.

How do scientists choose between competing phylogenetic hypotheses?

They compare their likelihoods and favor the hypothesis that makes the observed DNA data more likely.

In the lecture example, which hypothesis was most likely?

Hypothesis A because it had a likelihood score of 1.35 compared with 0.99 for hypotheses B and C.

Why can scientists not calculate the probability of every possible phylogenetic tree?

The number of possible evolutionary trees becomes too large to evaluate individually.

How do scientists handle the large number of possible phylogenetic trees?

They use efficient computational methods to search for the most likely hypotheses.

What observations helped Darwin develop the theory of natural selection?

Populations can grow exponentially, population sizes remain relatively stable, resources are limited, and traits are heritable.

Why do populations have the potential for exponential growth?

Organisms can produce more offspring than are necessary to replace themselves.

Why do population sizes tend to remain relatively stable?

Limited resources and environmental pressures prevent unlimited population growth.

Why are resources important in natural selection?

Limited resources create competition among organisms.

Why is heritability important to natural selection?

Favorable traits must be passed from parents to offspring for them to become more common over generations.

Which statement is an inference rather than an observation in Darwin's reasoning?

Species are well adapted to their ecological niches.

Systematics

The study of biological diversity and evolutionary relationships.

Taxonomy

The identifying, naming, and classifying of species.

Folk systematics

Classification systems developed outside a standardized scientific context.

Linnaean classification

A system of classification developed by Carl Linnaeus based on nested groups and scientific naming.

Carl Linnaeus

An eighteenth century naturalist who developed the classification system that influenced modern taxonomy.

Nested hierarchy

A classification system in which smaller groups are contained within larger groups.

Binomial nomenclature

A scientific naming system that gives each species a two part name consisting of its genus and specific epithet.

Genus

A taxonomic group containing one or more closely related species.

Specific epithet

The second part of a scientific species name that identifies a particular species within its genus.

Species

A group of organisms classified as a distinct biological group.

Clade

A monophyletic group consisting of an ancestor and all of its descendants.

Monophyletic group

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

Polyphyletic group

A group containing organisms from different evolutionary lineages without their most recent common ancestor.

Paraphyletic group

A group containing a common ancestor but not all of its descendants.

Biological Species Concept

A species concept defining species as natural populations that actually or potentially interbreed and are reproductively isolated from other such groups.

Speciation

The evolutionary process by which new species arise.

Reproductive isolation

The inability of populations to successfully exchange genes through reproduction.

Gene flow

The movement of genes between populations through reproduction.

Prezygotic isolation

Reproductive barriers that prevent mating or fertilization from occurring.

Postzygotic isolation

Reproductive barriers that reduce the survival or reproductive success of hybrid offspring after fertilization.

Hybrid

An offspring produced by parents from different species or genetically distinct populations.

F1 hybrid

The first generation of offspring produced by crossing two different parental lineages.

Intrinsic incompatibility

A reproductive barrier caused by genetic differences that interact poorly within hybrid offspring.

Extrinsic incompatibility

A reproductive barrier caused by environmental conditions that reduce hybrid fitness.

What are the two major contributions of Linnaean classification?

Nested hierarchy and binomial nomenclature.

What is the purpose of a nested hierarchy?

It organizes organisms into increasingly specific groups based on shared characteristics.

Why do species within the same genus tend to be closely related?

They share a more recent common ancestor than species belonging to different genera.

What are the two parts of a scientific species name?

Genus and specific epithet.

How is a scientific species name written?

The genus name is capitalized, the specific epithet is lowercase, and both are italicized.

Are two organisms with the same specific epithet necessarily closely related?

No, organisms in different genera can share a specific epithet.

Why is modern systematics based on monophyletic groups?

Monophyletic groups reflect evolutionary relationships and common ancestry.

Why are folk classification systems not always consistent with modern systematics?

They are often based on local needs and may not reflect evolutionary relationships.