Biology 101: Evolution and History of Life

BIOL 1P92 Course Information

• Course name: BIOL 1P92
• Course description: Introduction to Biology II
• Instructor: Dr. Szuroczki
• Co-ordinator: Katie Hunter ([email protected])
• Important contact for lab grades: Dr. Martin ([email protected])
• Required textbook: Biology 6e W/Connect (2 Years Access) Ed: 6
• Textbook authors: Brooker, Widmaier, Graham, Sti
• Textbook ISBN: 9781265396138
• Publisher: McGraw Hill
• Connect platform: Suggested but not required

Course Marking Scheme

• Midterm Test: 30% (Week 1-3 content covered by Dr. Szuroczki)
• Final Exam: 35%
• Laboratory assignments: 35%

Topic Schedule

• Chapter 22: Introduction to Evolution
• Chapter 23: Population Genetics (Microevolution)
• Chapter 26.1-26.2: History of Life on Earth
• Chapter 24: Origin of Species (Macroevolution)
• Chapter 25.1-25.3: Taxonomy & Phylogenetics
• Chapter 27-29: Biodiversity (Bacteria, Archaea, Protists, Fungi) in an Evolutionary Context
• Chapter 31: Evolution of Land Plants & Charophycean Algae
• Chapter 33: Animal Diversity & Choanoflagellates
• Chapter 34,35.1: The Invertebrates & Vertebrates
• Chapter 41,47.4: Animal Bodies & Homeostasis
• Chapter 42.1-42.4: Neuroscience

Key Concepts

• Overview of Evolution
• Evidence of Evolutionary Change
• The Molecular Processes that Underlie Evolution

Introduction and Definitions

• Evolution: Heritable change in one or more characteristics of a population or species from one generation to the next
• Microevolution: Viewed on a small scale; changes in a single gene or allele frequencies in a population over time
• Macroevolution: Viewed on a larger scale; Formation of new species or groups of related species
• Species: Group of related organisms that share a distinctive form
• Population: All members of the same species that live in the same area at the same time and have the opportunity to interbreed

Scientists Who Set the Stage

• John Ray (mid- to late-1600s): First to carry out a thorough study of the natural world, developed an early classification system.
• Carl Linnaeus: Extended John Ray's work to develop the binomial system of nomenclature (Homo sapiens).
• Georges Buffon: Suggested life forms change through time.
• Jean-Baptiste Lamarck: Hypothesized that species change over many generations by adapting to their environments (Inheritance of acquired characteristics).
• Erasmus Darwin: Early advocate of evolutionary change and suggested common ancestry.

Inheritance of Acquired Characteristics (Lamarck)

• Organisms change their behavior in response to environmental changes, modifying traits
• Modifications are then inherited by offspring
• Example: Giraffes stretching their necks to reach higher leaves, leading to longer necks in subsequent generations

Influence from Other Fields of Study

• Uniformitarianism: Slow geological processes lead to substantial change, Earth is older than 6,000 years
• Catastrophism: Belief that Earth's features are formed by short-lived violent events.
• Thomas Malthus: An economist whose essay on population growth (1798) showed that not all members of a population will survive and reproduce.

Charles Darwin

• Born in 1809
• Played a central role in developing the theory of evolution, suggesting that existing species evolved from pre-existing species.
• Key influence: Voyage on HMS Beagle (1831-1836), particularly observations of Galapagos finches.
• Theory of Evolution: Descent with modification through variation and natural selection (two interacting factors) - Variation: Traits varying in individuals and are heritable. Genetic basis not known at that time. - Natural selection: Individuals with traits better suited to the environment flourish and reproduce; others less likely
• Published On the Origin of Species in 1859
• Alfred Wallace: Sent Darwin an unpublished manuscript with similar ideas in 1858

Darwin's Theory of Evolution (in depth)

• Variation in traits: Individuals within a population vary in heritable traits
• Natural selection: Individuals better suited to the environment are more likely to survive and reproduce, passing traits to the next generation.
• Favorable traits increase in the population over time

Source of Genetic Variation

• Genetic variation: An important force in evolution because it allows natural selection
• Can be caused by mutation (creating new alleles)
• Random mating, random fertilization, and recombination during meiosis

Evolutionary adaptation by Natural Selection

• Natural selection favors traits that enhance survival and reproduction in a given environment
• Example: Galapagos finches - beak size adaptation as a response to seed availability
• Example: The evolution of finches adapting to larger seeds in a drought

Examples of Natural Selection

• Daphne Major: Medium ground finches; beak depth as a heritable trait was studied over 40 years; severe drought in 1977 resulted in fewer smaller seeds; offspring had larger beak size in 1978.

Selective Breeding

• Programs and procedures to modify traits in domesticated species
• Artificial selection: Breeders choose the parents with desirable traits
• Different from natural selection in the choice of parents

Example: Darwin's Pigeons

• Darwin studied rock pigeon varieties in his work "Variation in Animals and Plants under Domestication"
• Drawings of variations in pigeons

Example: Wild Mustard

• Illustrates how selective breeding can change traits in plants
• Wild mustard can be bred into different varieties (e.g., Kohlrabi, Kale, Broccoli, Brussels sprouts, Cabbage, Cauliflower)

Biogeography

• Study of the geographic distribution of extinct and living species
• Isolated continents and island groups have evolved distinct plant and animal communities
• Endemic Species: Naturally found only in a particular location. Ex: Island fox, evolved from mainland fox during ice ages

Example: Australia

• First mammals arose before Australia separated
• Australia has no native large terrestrial placental mammals but has marsupials.

Convergent Evolution

• Species from different lineages evolve similar characteristics because they occupy similar environments.
• Analogous structures and convergent traits are not similar due to shared evolutionary history.

Fossil Record

• Fossils are compared according to age (oldest to youngest)
• Reveals successive evolutionary change
• Transitional forms: Fossils providing a link between older and younger fossils/species.

Example: Fish-like Tetrapod (Tiktaalik roseae)

• Transitional form between fishes and tetrapods
• Characteristics: Broad skull, flexible neck, eyes on top of head, primitive wrist, finger-like bones
• Could peek above water and look for prey

Example: Evolution of Whales

• Order Cetacea (whales, dolphins, porpoises)
• Closest relatives: hippos
• Evolved from terrestrial tetrapods over 50 million years to aquatic animals without hind limbs.

Homology

• Fundamental similarity due to descent from a common ancestor
• Anatomical homology: Modern vertebrates have a similar set of bones in their forelimbs despite their different functions
• Developmental homology: Species that differ as adults often bear striking similarities during early embryonic development (e.g., gill ridges, bony tails). Examples of species from different lineages that share common development-related homologous structures: Lizard, Tortoise, Pig, Human
• Molecular homology: Similarities at the molecular level (e.g., DNA sequences, biochemical pathways) indicate that living species evolved from a common ancestor
• Homologous Genes:* Two or more genes derived from the same ancestral gene. In different species, they are called orthologs. Two sequences may be similar, but not identical, due to independent accumulation of different random mutations.
• Gene Families:* Two or more homologous genes in a single species; called paralogs. These are generated by gene duplication events within a genome of a single organism. An example is the globin family (myoglobin, cytoglobin, different forms of hemoglobin).

Horizontal Gene Transfer

• Organisms incorporate genetic material from other organisms without being offspring from those organisms
• Widespread among bacteria

Evolution at the Genome Level

• Evolutionary changes at the genome level involves changes in chromosome structure and number because these changes can influence the ability of two organisms to breed with another. This can also be an important factor in establishing new species.