Chapter 10 : Evolution

Interactive Study Notes Preview

Chapter Overview & SLOs

What is evolution? Chapter 10, "Evolution," examines the processes that drive the diversity of life on Earth over successive generations. This chapter answers fundamental questions about how species change over time and how new species arise. What is Darwin's theory of natural selection? You will learn Darwin's theory of natural selection based on four key principles: - Overproduction: Organisms produce more offspring than can possibly survive given limited resources (food, water, shelter). - Variation: Individuals within a population show differences in traits (size, color, speed, disease resistance). Variations arise from mutations and genetic recombination during sexual reproduction. - Competition: Individuals compete for limited resources. Those with advantageous traits are more likely to survive and reproduce. - Survival of the Fittest: Individuals with traits best suited to their environment survive longer and leave more offspring. Over many generations, favorable traits become more common in the population. What is the difference between natural selection and artificial selection? You will compare: - Natural Selection: Environmental factors determine which traits are advantageous. Process is slow, occurs naturally. Examples: antibiotic resistance in bacteria, industrial melanism in peppered moths, beak variations in Galapagos finches. - Artificial Selection (Selective Breeding): Humans select desirable traits and breed individuals with those traits. Process is faster, controlled by humans. Examples: crop improvement (larger grains, disease-resistant wheat), animal breeds (different dog breeds, high milk-yielding cows), ornamental plants (various rose and orchid varieties). What is the evidence for evolution? You will explore multiple lines of evidence for evolution: - Palaeontology (Fossil Evidence): Study of fossils (preserved remains of ancient organisms). Fossils show a progression of life forms over geological time. Transitional fossils like Tiktaalik (fish with limb-like fins, showing transition from water to land) provide evidence of gradual change. - Comparative Anatomy: - Homologous Organs: Same basic structure but different functions, indicating common ancestry. Example: Pentadactyl limb (five-digit structure) in humans (grasping), whale (swimming), bat (flying), horse (running). - Analogous Organs: Different structures but similar functions, indicating convergent evolution (unrelated species evolve similar traits due to similar environments). Example: Wings of birds and wings of insects. - Vestigial Organs: Structures that have lost their original function through evolution. Examples: human appendix (remnant of larger cecum for digesting cellulose), wisdom teeth (remnants of larger jaws in ancestors), tailbone (coccyx, remnant of tail), whale pelvic bones (remnants of hind limbs). - Comparative Embryology: Comparing embryonic development across different species. Closely related species show similar embryonic stages (e.g., all vertebrates have pharyngeal pouches and tails in early embryonic stages), indicating common ancestry. - Molecular Biology (Genetic Evidence): Comparing DNA and protein sequences. Closely related species have more similar DNA sequences. Humans and chimpanzees share approximately 98-99% of their DNA. - Biogeography: Geographical distribution of species. Closely related species are found near each other. Unique species on islands (Galapagos finches, Hawaiian honeycreepers) evolved from mainland ancestors. What is speciation and how does it occur? You will study the mechanisms of speciation (formation of new species): - Variations: Source of genetic diversity. Arise from mutations (changes in DNA sequence) and genetic recombination (shuffling of genes during sexual reproduction). - Allopatric Speciation: Physical barrier (mountain range, river, ocean) separates a population into two groups. Each group evolves independently and becomes reproductively isolated. Example: Darwin's finches on different Galapagos Islands. - Sympatric Speciation: New species evolve within the same geographical area. Often occurs due to polyploidy (extra sets of chromosomes) or habitat differentiation. Example: Cichlid fish in African lakes. - Parapatric Speciation: Adjacent populations evolve into new species without complete physical separation. Occurs along environmental gradients. Example: Grass species adapting to contaminated soil near mines. What are the key case studies of evolution? You will analyze: - Industrial Melanism in Peppered Moths (Biston betularia): Before industrial revolution, light-colored moths were common (camouflaged on lichen-covered trees). After pollution darkened tree bark, dark-colored moths became more common due to reduced predation. This demonstrates natural selection in action over a short time period. - Galapagos Finches (Darwin's Finches): Different finch species on Galapagos Islands evolved different beak shapes adapted to different food sources (seeds, insects, cactus flowers, blood). This demonstrates adaptive radiation (evolution of multiple species from common ancestor) and natural selection based on food availability. These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• What is evolution and what is Darwin's theory of natural selection? Define evolution (change in heritable traits of populations over generations) and explain the theory of natural selection based on the principles of overproduction (more offspring than can survive), variation (differences in traits within population), competition (for limited resources), and survival of the fittest (advantageous traits become more common over time).
• What is the evidence for evolution? Analyze evidence for evolution provided by the fossil record (palaeontology, transitional fossils like Tiktaalik), homologous structures across species (pentadactyl limb showing common ancestry), vestigial organs (human appendix, wisdom teeth, tailbone, whale pelvic bones), comparative embryology (similar embryonic stages in related species), molecular biology (DNA similarities), and biogeography (geographical distribution of species).
• What is speciation and how does it occur? Describe the process of speciation (formation of new species) and differentiate between allopatric speciation (physical barrier separates populations, e.g., Galapagos finches), sympatric speciation (new species evolve within same area, e.g., polyploidy), and parapatric speciation (adjacent populations evolve along environmental gradients).
• What are the differences between natural selection and artificial selection? Contrast natural selection (environment determines advantageous traits, slow process, examples: industrial melanism in peppered moths, Galapagos finches) with artificial selection (humans select desirable traits, faster process, examples: selective breeding in agriculture for crop yield and animal husbandry for milk production and specific breeds).

Frequently Asked Questions (FAQ)