BI111 CH. 16,18,20.4,23 Final Exam

Morphological Species Concept

Defines species based on shared measurable traits. Useful for identifying fossils and species in the field but can be unreliable when individuals of the same species vary greatly or when different species look alike.

Biological Species Concept

Defines species as interbreeding populations that produce fertile offspring and are reproductively isolated from others. Highlights genetic cohesiveness within species and genetic distinctness between species. Does not apply to asexual or extinct organisms.

Phylogenetic Species Concept

Defines species as the smallest group of organisms that share a common ancestor. Uses genetic and morphological data, making it applicable to extinct and asexual species, but is limited by incomplete evolutionary histories.

Subspecies

Local variants of a species that show distinct genetic and phenotypic differences due to geographical separation. Neighboring subspecies may interbreed where their ranges overlap, producing intermediate traits.

Geographical Variation in Species

Populations of the same species can differ due to their environment and limited gene flow. Neighboring populations often share traits, while distant populations evolve distinct characteristics due to different selection pressures.

Ring Species

Species with a ring-shaped geographical distribution around an uninhabitable area. Adjacent populations interbreed, but distant populations may not. Example: Ensatina eschscholtzii salamanders in California.

Clinal Variation

Gradual change in a trait across a geographical gradient due to environmental differences. Example: House sparrows in colder regions have larger bodies to conserve heat.

Prezygotic Isolating Mechanisms

Barriers that prevent fertilization, maintaining species separation. Includes ecological, temporal, behavioral, mechanical, and gametic isolation.

Ecological Isolation

Species live in different habitats and do not meet. Example: Lions in open grasslands and tigers in dense forests.

Temporal Isolation

Species breed at different times. Example: Drosophila persimilis mates in the morning, Drosophila pseudoobscura in the afternoon.

Behavioral Isolation

Species do not recognize each other's courtship signals. Example: Fireflies of different species have distinct flashing patterns.

Mechanical Isolation

Structural differences prevent mating. Example: Mimulus lewisii is pollinated by bumblebees, while Mimulus cardinalis is pollinated by hummingbirds.

Gametic Isolation

A prezygotic barrier where sperm and eggs of different species cannot fuse due to incompatible surface proteins or physiological conditions.

Postzygotic Isolating Mechanisms

Barriers that reduce the fitness of hybrid offspring, preventing gene flow between species even if fertilization occurs.

Hybrid Inviability

A postzygotic barrier where hybrid embryos fail to develop or die at an early stage due to genetic incompatibilities.

Hybrid Sterility

A postzygotic barrier where hybrid individuals are unable to produce viable gametes due to mismatched chromosomes, preventing reproduction.

Hybrid Breakdown

A postzygotic barrier where F1 hybrids are fertile, but their offspring (F2 generation) have reduced survival or fertility.

Allopatric Speciation

The formation of new species due to geographical separation, which prevents gene flow and leads to genetic divergence.

Founder Effect

A type of genetic drift where a small, isolated population develops unique traits due to limited genetic variation from the original population.

Species Cluster

A group of closely related species that evolved from a common ancestor, often due to repeated colonization and isolation.

Secondary Contact

When two previously separated populations come back into contact, testing whether they have become reproductively isolated.

Hybrid Zone

A region where two species interbreed and produce hybrids, often maintained by environmental or genetic factors.

Reinforcement

The process where natural selection strengthens prezygotic barriers in response to low hybrid fitness, reducing hybrid formation.

Sympatric Speciation

Reproductive isolation evolves within a single population without geographic or environmental separation.

Host Race

A subpopulation that arises when a mutation causes individuals to prefer a new host plant, leading to ecological isolation.

Ecological Isolation

A form of reproductive isolation where subpopulations prefer different habitats or resources, limiting interbreeding.

Apple Maggot (Rhagoletis pomonella)

An example of possible sympatric speciation, where host races feeding on apples, hawthorns, and cherries show ecological and temporal isolation.

Disruptive Selection

A form of natural selection that favors extreme traits, driving genetic divergence between subpopulations.

Polyploidy

A genetic phenomenon where individuals have extra sets of chromosomes, leading to reproductive isolation and speciation, especially in plants.

Autopolyploidy

A type of polyploidy where chromosome duplication occurs within a single species, leading to reproductive isolation from the parent population.

Allopolyploidy

A type of polyploidy resulting from hybridization between species, where chromosome doubling restores fertility and leads to a new species.

Genetic Divergence

The accumulation of genetic differences between populations due to mutation, genetic drift, and natural selection, leading to reproductive isolation.

Postzygotic Isolation

Reproductive isolation occurring after fertilization, often due to hybrid sterility or inviability caused by genetic incompatibilities.

Prezygotic Isolation

Reproductive barriers that prevent fertilization, such as differences in mating behavior, mechanical incompatibilities, or ecological separation.

Sexual Selection and Speciation

The evolution of exaggerated traits in sexually dimorphic species can drive reproductive isolation and increase speciation rates.

Chromosome Alterations and Speciation

Changes in chromosome structure or number, such as inversions, translocations, deletions, and duplications, can contribute to speciation by causing reproductive isolation between closely related species.

Chromosome Banding Patterns

Banding patterns in stained chromosomes are used to identify and compare specific chromosome segments across species, aiding in the study of evolutionary relationships and chromosome structure.

Human Chromosome 2 Fusion

Humans have 46 chromosomes due to the fusion of two ancestral chromosomes into chromosome 2, while chimpanzees, gorillas, and orangutans have 48 chromosomes with separate ancestral chromosomes.

Chromosome Inversions

Chromosome inversions occur when a segment of a chromosome is reversed, affecting gene order and contributing to differences between species, such as between humans and other great apes.

Protein Evolution in Rearranged Chromosomes

Protein-coding genes in rearranged chromosome segments evolve faster than those in non-rearranged segments, contributing to genetic divergence and potentially fostering speciation.

Speciation Triggered by Chromosome Rearrangements

Chromosome rearrangements can accelerate speciation by inhibiting chromosome pairing and recombination, which leads to genetic divergence and reproductive isolation over time.

Chromosomal Comparison in Great Apes

Chromosomal differences, particularly in chromosome 2, contribute to reproductive isolation between humans and other great apes (chimpanzees, gorillas, and orangutans) due to structural variations.

Observational Research on Chromosomal Differences

Researchers used Giemsa staining to analyze banding patterns and confirmed that human chromosome 2 resulted from the fusion of two smaller chromosomes, a feature not found in chimpanzees, gorillas, or orangutans.

Antibiotic Resistance

Evolution by natural selection in bacteria that leads to resistance against antibiotics, often due to overuse or misuse of drugs.

Evolution

Gradual change in populations of organisms over generations, driven by environmental factors, leading to new traits and species.

Descent with Modification

Evolutionary process where all species share a common ancestor and change over time due to environmental pressures.

Natural Selection

Process where organisms with advantageous traits have a higher chance of survival and reproduction, leading to increased frequency of those traits.

Artificial Selection

Human-driven evolutionary change where individuals with desirable traits are selected for reproduction, enhancing those traits in future generations.

Population

A group of interbreeding individuals of a species that live together in a specific area.

Adaptation

Heritable trait that improves an organism's chances of survival and reproduction in its environment.

Fitness

An organism's ability to survive and reproduce, contributing offspring that survive to reproduce as well.

Galápagos Mockingbirds

Example of natural selection, where different mockingbird species evolved on separate islands from a common ancestor, adapting to local conditions.

Fitness (Evolution)

The reproductive success of an individual compared to others in the population, influenced by traits that increase survival and reproduction.

Variation

Genetic differences among individuals in a population, which provide the raw material for natural selection.

Differential Reproduction

When some individuals in a population reproduce more successfully due to advantageous traits, leading to those traits becoming more common.

Source of Variation in a Population

The source of variation in a population is random mutation, which is a heritable change in the DNA sequence.

How do mutations contribute to evolution?

Mutations provide the raw material for natural selection by introducing genetic differences, but they do not determine the path of evolution, as they are undirected and random.

Role of Mutations in Natural Selection

Mutations create genetic differences among organisms, which can be beneficial, harmful, or neutral. Natural selection then acts on these variations, favoring beneficial mutations.

What is natural selection?

Natural selection is the process where heritable variation in traits leads to differential survival and reproduction, shaping evolutionary change over time.

Effect of Industrial Pollution on Peppered Moths

Industrial pollution darkened tree bark, favoring darker moths (carbonaria) because they were less visible to predators, leading to an increase in their population.

What triggered the color change in peppered moths during the Industrial Revolution?

The color change in peppered moths during the Industrial Revolution was triggered by industrial pollution that darkened tree bark.

Tree Bark Darkening

The increase in pollution caused tree bark to darken, which favored darker moths (carbonaria) and increased their survival rate.

Color Variation in Peppered Moths

The color variation in peppered moths is due to a transposable element in the genome that increases melanin production in the dark (carbonaria) variety.

Freshwater vs Marine Sticklebacks

Freshwater sticklebacks have reduced or no armor and smaller spines compared to marine sticklebacks, as reduced armor increases fitness by reducing predation from dragonfly larvae and metabolic costs.

Pitx1 Gene

The gene Pitx1 regulates the development of pelvic spines in sticklebacks, with its expression being suppressed in freshwater populations, leading to reduced spine development.

Convergent Evolution

Convergent evolution is the independent evolution of similar traits in unrelated species due to similar environmental pressures, such as insects evolving the ability to tolerate cardenolides.

Insects and Cardenolides

Insects have evolved mutations that allow them to ingest cardenolides, which are toxic to most insects, making them distasteful to predators.

Bacteria Adaptation Speed

Bacteria have shorter generation times, allowing them to evolve and adapt more quickly than humans, who have longer generation times.

Experimental Evolution

Experimental evolution involves studying the evolutionary processes in real time by allowing organisms with short generation times, like bacteria, to evolve under controlled conditions.

E. coli Experiment

The E. coli experiment measured fitness by comparing growth rates of evolved and ancestral populations under different temperature conditions, with faster growth indicating higher fitness.

Fitness in Evolutionary Biology

Fitness in evolutionary biology refers to an organism's ability to survive, reproduce, and pass on its genes to the next generation.

Scala Naturae

Aristotle's classification system called Scala Naturae (Scale of Nature).

Hierarchy of Life in Scala Naturae

Organisms occupy a specific step on a ladder from the non-living world to humans, angels, and ultimately, God.

Aristotle's Classification System Merge

It was combined with the biblical account of creation, leading to the belief that organisms were specially created by God, could not change, and could not become extinct.

Natural Theology Proponent

Carolus Linnaeus was a major proponent of natural theology in the 18th century.

Linnaeus's Classification System

The binomial species classification system was introduced by Carolus Linnaeus for classifying organisms.

Linnaeus's View on Organism Similarity

He attributed the similarity to God's design, not to evolutionary relationships.

Natural Theology Focus

The belief that the study of nature provided evidence for the existence of God was the primary focus of natural theology during Linnaeus's time.

Indigenous Peoples Plant Classification

Some Indigenous Peoples named plants based on their appearance, growth form, and uses by humans, such as the soapberry, which was named after its frothing properties.

Jean Baptiste de Lamarck

French naturalist who proposed the first comprehensive theory of evolution in the 18th century, including the idea that acquired traits could be inherited, which was later disproven.

Lamarckian Inheritance

The incorrect hypothesis that traits acquired during an organism's lifetime can be passed on to offspring.

Spontaneous Generation

The idea, popular in Lamarck's time, that simple life forms could arise from nonliving material, like mice from dew on plants.

Charles Darwin

British naturalist who proposed the theory of evolution by natural selection, based on extensive observations and research during his voyage on the HMS Beagle.

HMS Beagle

The naval surveying ship on which Charles Darwin traveled for five years, collecting specimens and observing various habitats to support his theories of evolution.

Charles Lyell's 'Principles of Geology'

A foundational text that influenced Darwin, arguing that Earth's geology changes over long periods due to natural processes, challenging the idea of a static Earth.

Fossil Record

Evidence that some species have gone extinct, which suggested to Darwin that species could change or disappear over time, supporting his theory of evolution.

Biogeography

The study of the distribution of species across geographic areas, which led Darwin to hypothesize that species change over time based on their environment and location.

Galápagos Islands

An archipelago that greatly influenced Darwin's thinking, where he observed slight variations in species across different islands, suggesting they evolved from a common ancestor.

Homology

Similarity in structures among different species due to shared ancestry, such as the similar bone structures in the limbs of humans, seals, and bats.

Vestigial Structures

Body parts that no longer serve their original function, but may have been useful in ancestral species, as noted by Buffon and later incorporated into Darwin's theory.

Alfred Russel Wallace

A naturalist who independently developed a theory of evolution by natural selection, and whose work prompted Darwin to publish On the Origin of Species in 1859.

'On the Origin of Species'

Darwin's groundbreaking 1859 book that proposed natural selection as the mechanism of evolution, significantly changing the understanding of biological diversity.

Alfred Russel Wallace's trip to the Malay Archipelago

He collected 125,660 specimens, including more than 5,000 species new to science.

Wallace and Darwin's view of each other's work

They had strong respect and admiration for each other, and Wallace frequently admitted that Darwin's ideas were more thoroughly developed.

Wallace's reaction to Darwin's publication

Wallace was not upset and admitted that Darwin's ideas were better supported.

Struggle for existence

The competition among organisms for limited resources, leading to natural selection.

Thomas Malthus's theory about population growth

He argued that populations grow exponentially while food supply grows arithmetically, leading to inevitable poverty and starvation.

Influence of Malthus's ideas on Darwin and Wallace

Malthus's theory helped Darwin and Wallace understand that populations of organisms face competition for limited resources, leading to natural selection.

Role of Malthus's work in Darwin's theory

It helped clarify how the imbalance between population growth and food supply applied to plants and animals in nature.

modern synthesis in evolutionary biology

A unified theory of evolution that integrates genetics, paleontology, biogeography, and other disciplines within an evolutionary framework.