Evolution and Aristotle's Perspectives

The gradual change in the genetic makeup of a population over time, leading to new species arising from ancestral ones.

The process by which individuals with heritable traits that make them better suited to their environment survive and reproduce more successfully, passing on those traits.

Charles Darwin, an English naturalist who observed various adaptations of plants and animals during his voyage on the H.M.S. Beagle.

An inherited characteristic that enhances an organism's survival and reproduction in a specific environment.

1. Overproduction of offspring 2) Availability of resources / competition 3) Variation in population 4) Differential reproductive success / Selection -> Adaptation

An individual's reproductive success, measured by how many offspring they produce that survive to reproduce.

Genetic variation provides the raw material for natural selection to act upon. Individuals with advantageous variations are more likely to survive and reproduce, leading to a gradual change in the population.

Natural selection acts on individuals, favoring those with advantageous traits. However, it is the population that evolves over time, as the frequency of advantageous traits increases.

Structures in different species that share a common ancestry, but may have different functions.

The process where groups from a common ancestor evolve and accumulate differences, leading to new species.

Structures in different species that have similar functions, but evolved independently from different ancestors.

The independent evolution of similar features in distantly related organisms, often due to adaptation to similar environments.

The fossil record provides a chronological sequence of life forms, showing how species have changed over time and supporting the idea of common ancestry.

The study of the distribution of species across the globe, revealing patterns that support evolutionary relationships.

Structures that are seemingly useless in a modern organism, but represent remnants of functional structures in their ancestors.

Natural selection is the mechanism by which evolution occurs. Evolution is the gradual change in the genetic makeup of a population over time, while natural selection is the process that drives this change by favoring individuals with advantageous traits.

Natural selection can only work with the existing variations within a population. New adaptations arise through chance mutations. Additionally, historical constraints and compromises limit the perfection of adaptations.

The peppered moth example vividly demonstrates how natural selection can lead to rapid changes in a population's traits in response to environmental changes.

The evolution of antibiotic resistance in bacteria highlights the impact of human actions on evolution. Overusing antibiotics selects for resistant strains, posing a major threat to public health.

Soapberry bugs provide evidence for natural selection, illustrating how beak length adapts to the size of the fruit they feed on.

Darwin was influenced by the works of Hutton & Lyell on geology, Malthus on population growth, and the practice of artificial selection.

His observations of diverse adaptations in different environments, particularly on the Galapagos Islands, provided critical evidence for the idea of natural selection.

Lamarck believed that traits acquired during an organism's lifetime could be inherited. Darwin, however, proposed that individuals with advantageous traits are more likely to survive and reproduce, passing on those traits.

A hierarchical view of life that places organisms on a scale of increasing complexity, with humans occupying the highest position.

Evolutionary biology does not support the concept of higher and lower organisms. All organisms are equally evolved but through different selection pressures.

Natural selection explains that all life forms share common ancestry (unity), but have adapted to different environments, leading to the diversity of life.

Adaptation is the product of natural selection, which favors traits that enhance survival and reproduction in a given environment.

Chance events, such as mutations and environmental changes, play a role in evolution by introducing new variations and shaping the direction of natural selection.

The genetic makeup of an organism, represented by letters. Each letter signifies a specific allele.

The observable physical characteristics of an organism, resulting from the genotype.

An organism that has two identical alleles for a particular trait.

An organism that has two different alleles for a particular trait.

Genetic variation provides the raw material for natural selection to act upon. Different alleles lead to different traits, which can be advantageous or disadvantageous in certain environments.

The total genetic diversity within a population. It encompasses all the alleles present in that population.

Higher genetic diversity means more alleles are present in a population, increasing the chances of having individuals with beneficial traits for adaptation to environmental changes.

It's the core concept of evolution, which states that organisms evolve from their ancestors by gradually accumulating changes in their traits over generations.

A population is a group of individuals of the same species living in the same area at the same time.

Evolution is driven by changes in gene frequencies, which are influenced by various mechanisms like mutation, natural selection, gene flow, and genetic drift.

A gene is a segment of DNA that contains the instructions for a specific trait.

Alleles are different forms of a gene.

A change in the genetic makeup of a population from one generation to the next. It involves the evolutionary changes within a species.

The proportion of a specific genotype (combination of alleles) in a population. For example, if 50% of a population has the genotype AA, then the genotype frequency for AA is 0.5.

The proportion of a specific allele (version of a gene) within a population. For example, if 70% of the alleles in a population are 'A', then the allele frequency for 'A' is 0.7.

A state where the frequencies of alleles and genotypes remain stable across generations, indicating no evolutionary change within a population.

During a drought, finches with larger beaks had a survival advantage as they could crack larger, harder seeds. Consequently, the population evolved by natural selection, favoring large beaked birds and shifting the allele frequency towards traits beneficial for that environment.

Genetic equilibrium can be disrupted by factors such as mutations, gene flow, genetic drift, and natural selection, all of which introduce genetic changes within a population.

Microevolution serves as the foundation for larger evolutionary changes, showcasing how populations adapt to their environment and eventually leading to the emergence of new species over time.

Understanding microevolution helps us grasp the dynamic nature of life on Earth, including the evolution of adaptations, resistance to diseases, and the potential for future evolutionary changes.

A state where the allele frequencies of a population remain constant from one generation to the next. This means the population is not evolving with respect to the gene or trait being studied.

The change in allele frequencies within a population over generations. This indicates that the population is evolving.

It states that in a large, randomly mating population, allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences.

1. Large population size: Prevents genetic drift. 2. Random mating: No preference for specific traits. 3. No mutations: No new alleles introduced. 4. No gene flow: No migration of individuals in or out. 5. No natural selection: All genotypes have equal survival and reproductive rates.

It provides a theoretical framework for understanding how populations evolve. By comparing real-world populations to the ideal conditions of Hardy-Weinberg, we can identify the evolutionary forces at play.

The equation is p^2 + 2pq + q^2 = 1, where p represents the frequency of one allele and q represents the frequency of the other allele. You can use observed genotype frequencies to calculate these allele frequencies.

By comparing allele frequencies over time, scientists can determine if a population is evolving and identify the factors that are causing the changes.

It helps us to understand the genetic basis of diseases, predict the impact of conservation measures, and monitor the effects of environmental changes on populations.

Natural selection is the process by which individuals with advantageous traits survive and reproduce more successfully, leading to the gradual increase in the frequency of those traits in a population. Adaptation is the result of natural selection, representing the traits that have become more common due to their survival and reproductive benefits.

Mutation rates, the frequency of changes in DNA sequences, differ significantly between different types of organisms. Generally, microorganisms tend to have higher mutation rates compared to plants and animals. This is because microorganisms have shorter generation times, meaning mutations accumulate more quickly.

Natural selection acts on the phenotypes (observable traits) of individuals within a population. By favoring individuals with traits that increase their survival and reproduction, natural selection indirectly influences the allele frequencies in the population. Alleles that contribute to advantageous traits become more common, while those associated with less favorable traits may decrease in frequency over time.

Genetic drift is the random fluctuation of allele frequencies in a population due to chance events. These events, such as natural disasters or small population sizes, can cause certain alleles to become more or less common, regardless of their effects on survival and reproduction. The smaller the population, the greater the impact of genetic drift.

Natural selection is the driving force behind adaptation. It favors individuals with traits that are better suited to their environment, increasing their chances of survival and reproduction. Over time, the beneficial traits become more common in the population, leading to a gradual change in the species that makes it better adapted to its environment.

In the equation, p represents the frequency of the dominant allele and q represents the frequency of the recessive allele.

The genotype frequencies are calculated using the equation: p² + 2pq + q² = 1, where p² represents the frequency of homozygous dominant, 2pq represents the frequency of heterozygous, and q² represents the frequency of homozygous recessive.

Allele frequencies (p and q) are calculated by dividing the number of each allele by the total number of alleles in the population.

The Hardy-Weinberg Principle provides a baseline for understanding evolution. By comparing real populations to the equilibrium, we can identify which evolutionary forces are acting on the population.

Deviations from the Hardy-Weinberg equilibrium indicate evolutionary change. By analyzing these deviations, we can identify the specific evolutionary forces driving the change.

The Hardy-Weinberg Principle emphasizes that populations remain stable in the absence of evolutionary forces, including natural selection. Natural selection is one of the driving forces that can cause deviations from this equilibrium.

A species is a group of populations whose members can interbreed in nature and produce viable, fertile offspring.

Mechanisms that prevent members of different species from interbreeding, ensuring they remain distinct.

Reproductive barriers that block fertilization from occurring, like habitat isolation, temporal isolation, etc.

Reproductive barriers that prevent a hybrid zygote from developing into a viable, fertile adult, like reduced hybrid viability, etc.

Habitat isolation (different environments), temporal isolation (different breeding times), behavioral isolation (mating rituals), mechanical isolation (incompatible reproductive parts), gametic isolation (sperm and egg incompatibility).

Reduced hybrid viability (hybrid offspring have low survival), reduced hybrid fertility (hybrids cannot reproduce), hybrid breakdown (first generation hybrids are fertile, but their offspring are infertile).

Reproductive isolation is essential for speciation, as it prevents gene flow between populations and allows them to evolve independently.

A prezygotic barrier where species cannot interbreed due to differences in their courtship rituals, mating displays, or other behaviors unique to each species.

Any barrier that prevents mating or fertilization from occurring between species. They act before the formation of a zygote.

A prezygotic barrier where physical incompatibility between reproductive structures prevents successful mating.

A prezygotic barrier where the sperm of one species cannot fertilize the eggs of another species.

A prezygotic barrier where species live in different habitats or geographical locations, preventing interbreeding.

When populations are separated by different habitats, they experience different selective pressures and genetic drift. These differences accumulate over time leading to genetic divergence and eventually, the formation of distinct species.

The evolutionary process by which new species arise from existing ones.

The five prezygotic barriers are: Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, and Gametic Isolation.

A postzygotic barrier where the offspring of two different species is unable to develop or survive due to incompatible genes.

A postzygotic barrier where the offspring of two different species is healthy but sterile, meaning it cannot reproduce.

A postzygotic barrier where the offspring of a hybrid can reproduce, but their offspring are weak or sterile.

A reproductive barrier that prevents a hybrid from developing into a viable, fertile adult. It acts after the formation of a hybrid zygote.

It cannot be applied to asexual organisms, organisms about which little is known regarding their reproduction, or fossils.

Genetic drift can cause the genetic differences between two populations to increase, eventually leading to speciation.

It cannot be applied to asexual organisms, organisms about which little is known regarding their reproduction, or fossils.

Defines a species based on its physical characteristics, such as body shape, size, and other structural features. This concept applies to both asexual and sexual organisms.

Defines a species based on its ecological niche, which includes its interactions with the environment and its role within the ecosystem.

Defines a species based on its evolutionary history, traced through genetic comparisons, particularly DNA sequences.

Speciation that occurs when two populations are geographically separated, preventing gene flow and allowing them to evolve independently.

Speciation that occurs within a geographically overlapping population, often driven by biological factors like chromosomal changes or non-random mating.

Any mechanism that prevents individuals of different species from interbreeding and producing viable offspring.

A reproductive barrier that prevents fertilization from occurring between individuals of different species.

A reproductive barrier that acts after fertilization, preventing a hybrid zygote from developing into a viable, fertile offspring.

A polytomy occurs on an evolutionary tree when a node has more than two lineages descending from a single ancestor. This could indicate uncertainty about the relationships between descendants or simultaneous speciation.

A monophyletic group, also known as a clade, includes a common ancestor and all of its descendants. It is characterized by a single evolutionary origin.

A paraphyletic group includes a common ancestor but not all of its descendants. It excludes one or more descendant lineages.

The oldest species are at the bottom (or left) of the tree, while the most recent species are at the top (or right). Time progresses upwards.

Rotating branches around a node doesn't change the relationships depicted on the tree. It only changes the spatial arrangement, not the order of divergence.

A useful character for building a phylogeny must vary among different species, but not within the same species. This means the character is useful for distinguishing between species but not between individuals within a species. For example, the presence or absence of wings would be a useful character, but the color of the wings might not be because wings are different among species, but wing color can vary among individuals within the same species.

Sometimes, taxonomists might place a species within a genus that it's not most closely related to due to historical reasons, lack of sufficient data, or even misinterpretations of the species' characteristics. Over time, as more data and understanding becomes available, these classifications may be revised.

Molecular phylogeny involves comparing DNA sequences from different organisms. By analyzing the similarities and differences in these sequences, we can reconstruct evolutionary relationships between organisms.

The process of using molecular data for building phylogenetic trees is conceptually similar to using morphological data. We start by sequencing DNA, then align sequences to compare similar regions. The more similar the sequences, the more closely related the species.

Sister taxa refer to groups of organisms that share a common ancestor that is not shared by any other group. Imagine a family tree; siblings would be considered sister taxa.

A basal taxon in a phylogenetic tree represents a lineage that evolved early on and remains unbranched. It's like the original ancestor that gave rise to the other groups represented in the tree.