bio Flashcards Set

Introduction to Evolutionary Evidence

Paleontology and Fossils

• Paleontology is the scientific study of fossils, which are the preserved remains or traces of ancient life forms, providing crucial insights into the history of life on Earth.

• Transitional forms are fossils that exhibit traits common to both an ancestral group and its derived descendant group, illustrating the gradual changes that occur over time. An example is the Archaeopteryx, which shows features of both dinosaurs and modern birds.

• The fossil record serves as a timeline of evolutionary history, documenting the emergence and extinction of species, and revealing patterns of evolution over millions of years.

Homology and Developmental Biology

• Homology refers to similarities in structures or genes across different species due to shared ancestry, such as the forelimbs of mammals, which have different functions but similar bone structures.

• Embryonic homologies are observed in the early developmental stages of vertebrates, where structures like tails and pharyngeal pouches are present, indicating a common ancestry among diverse species.

• Vestigial organs are remnants of structures that had important functions in ancestors but are reduced or nonfunctional in modern descendants, such as the human appendix, which is a vestige of a larger cecum used for digesting cellulose.

Evolutionary Mechanisms

• Convergent evolution occurs when unrelated species develop similar traits due to adapting to similar environments, such as the wings of bats and birds, which evolved independently but serve the same function.

• Divergent evolution describes the process where two related species become more dissimilar over time, often due to different environmental pressures, leading to speciation.

• Biogeography studies the distribution of species across geographical areas, providing insights into how geographical barriers and historical events shape evolutionary paths.

Speciation and Natural Selection

Types of Speciation

• Allopatric speciation occurs when populations are geographically isolated, leading to the development of new species due to the lack of gene flow, as seen in Darwin's finches on the Galápagos Islands.

• Sympatric speciation is rarer and occurs without geographical barriers, often driven by ecological niches or behavioral differences, such as variations in mating calls among frogs.

• The Biological Species Concept defines species as groups of organisms that can interbreed and produce fertile offspring, emphasizing reproductive isolation as a key factor in speciation.

Natural Selection and Evolutionary Theory

• Natural selection is the process by which individuals with favorable traits are more likely to survive and reproduce, leading to the gradual evolution of species over generations.

• The five tenets of evolution include variation in populations, inheritance of traits, competition for resources, survival of the fittest, and evolution occurring over time.

• Types of natural selection include directional selection (favoring one extreme phenotype), stabilizing selection (favoring intermediate phenotypes), and disruptive selection (favoring both extremes).

Genetic Mechanisms and Evolutionary Processes

Genetic Variation and Evolution

• Recombination is the process by which genetic material is shuffled during reproduction, leading to offspring with new combinations of traits, enhancing genetic diversity.

• Mutations are random changes in the genetic code that can introduce new traits into a population, serving as a raw material for evolution.

• Gene flow refers to the transfer of genes between populations through migration, which can introduce new genetic material and increase diversity.

Genetic Drift and Its Effects

• Genetic drift is the random fluctuation of allele frequencies in small populations, which can lead to significant changes over time, especially in isolated groups.

• The bottleneck effect occurs when a population's size is drastically reduced due to environmental events, leading to a loss of genetic diversity.

• The founder effect happens when a small group establishes a new population, resulting in reduced genetic variation compared to the original population.

Phylogenetics and Cladistics

Understanding Phylogenetic Relationships

• Phylogenetics is the study of evolutionary relationships among species, often represented through phylogenetic trees that illustrate these connections over time.

• Cladistics is a method of classification based on shared derived characteristics, grouping organisms according to their evolutionary history.

• Monophyletic groups include a common ancestor and all its descendants, while polyphyletic groups consist of organisms from different ancestors, and paraphyletic groups include a common ancestor but not all descendants.

Key Concepts in Cladistics

• Synapomorphy refers to a shared, derived trait that is used to group species, providing evidence of common ancestry.

• The principle of parsimony suggests that the simplest explanation, requiring the fewest evolutionary changes, is preferred when constructing phylogenetic trees.

• Outgroups are species or groups that are closely related to the group being studied but are not part of it, helping to determine the evolutionary relationships within the group.

1. 5 Tenets of Evolution:

• Variation: Individuals in a population are different.

  • Inheritance: Traits are passed from parents to offspring.

  • Overproduction: More offspring are produced than can survive.

  • Differential Survival & Reproduction: Individuals with favorable traits are more likely to survive and reproduce.

  • Adaptation: Over time, favorable traits become more common in the population.

2. Fitness in Evolution:
   Fitness refers to an organism’s ability to survive and reproduce, passing on its genes to the next generation.

3. Causes of Evolution:

• Major: Natural selection, sexual selection.

  • Minor: Mutation (changes in DNA), genetic drift (random changes), gene flow (movement of genes between populations).

4. Recombination & Mutation:

• Recombination: Genetic material is shuffled during reproduction, creating genetic diversity.

  • Mutation: Random changes in DNA that can introduce new traits.

5. Natural Selection & Sexual Selection:

• Natural selection: Organisms with traits that help them survive are more likely to reproduce.

  • Sexual selection: Traits that make an organism more attractive to mates increase the chances of reproduction.

6. Gene Flow: The movement of genes between populations through migration or interbreeding, mixing the gene pools.

7. Genetic Drift: Random changes in allele frequencies, especially in small populations. Types:

• Bottleneck effect: A drastic reduction in population size reduces genetic diversity.

  • Founder effect: A small group starts a new population with limited genetic diversity.

8. Biological Species Concept: Species are defined as groups of interbreeding populations that are reproductively isolated from other such groups.

9. Reproductive Isolation (Types):

• Prezygotic: Barriers before fertilization (e.g., behavioral, temporal, mechanical).

  • Postzygotic: Barriers after fertilization (e.g., hybrid inviability, hybrid sterility).

10. 4 Types of Evidence for Evolution:

• Direct Observation: Watching evolution happen (e.g., bacteria resistance).

• Biogeography: Distribution of species across the world.

• Homology: Similar structures due to shared ancestry (e.g., human arm, whale fin).

• Fossil Record: Evidence of past life forms showing changes over time.

11. Phylogenetics: Organizing organisms based on their evolutionary relationships (family tree of life). It shows how species are related through common ancestors.

Why Traits Evolve:
Traits evolve because they help organisms survive and reproduce in their environment. Evolution from a common ancestor leads to diverse forms that adapt to different challenges, ensuring survival of life in changing conditions.

How do transitional forms in the fossil record provide evidence for evolution?

Transitional forms serve as crucial evidence for evolution by illustrating the gradual changes that occur between different species over time. These fossils highlight intermediate states, demonstrating how species adapt and evolve, thus supporting the theory of common ancestry.

What is the significance of homologous structures in understanding evolutionary relationships?

Homologous structures indicate a common evolutionary origin among different species, despite their varied functions. This similarity in anatomy reinforces the concept of descent with modification, showcasing how species diverge from a shared ancestor while adapting to different environments.

In what ways do natural selection and artificial selection differ in their mechanisms and outcomes?

Natural selection operates through environmental pressures favoring advantageous traits, leading to adaptations that enhance survival and reproduction. In contrast, artificial selection is driven by human preferences, often resulting in traits that may not necessarily confer survival advantages in the wild.

Discuss the role of genetic drift in small populations and its potential impact on evolution.

Genetic drift can significantly affect small populations by causing random fluctuations in allele frequencies, which may lead to reduced genetic diversity and increased vulnerability to extinction. Events like the bottleneck effect and founder effect exemplify how chance events can shape the genetic landscape of populations over time.

How do the concepts of convergent and divergent evolution illustrate different evolutionary processes?

Convergent evolution occurs when unrelated species develop similar traits due to analogous environmental pressures, while divergent evolution happens when related species become more distinct over time. These processes highlight the adaptive nature of evolution, demonstrating how organisms respond to their environments in varied ways.

What evidence supports the theory of evolution, and how do these forms of evidence interrelate?

Evidence for evolution includes the fossil record, biogeography, homology, and direct observation, each providing unique insights into evolutionary processes. Together, these forms of evidence create a comprehensive understanding of how species evolve, adapt, and share common ancestry, reinforcing the validity of evolutionary theory.