Human Evolution (cont.)

Human Evolution

Theories of Modern Human Appearance

• Out of Africa Hypothesis

  • Modern humans (Homo sapiens) first emerged in Africa.

  • They later spread across the globe.

• Multiregional HypothesisHuman Evolution (cont.)

  • Suggests early human subgroups appeared simultaneously in Africa, Asia, and Europe.

  • These subgroups interbred, leading to the emergence of modern humans.

Neanderthals

• Existed approximately 330,000 to 30,000 years ago

• Exclusively resided in Europe.

• Complete DNA from a 38,000-year-old fossil has been sequenced.

Fossil Record of Human Evolution

• Australopithecus

  • Lived around 4.4 million years ago in Africa.

  • Famous Fossil: "Lucy"

    • Height: ~4.5 feet tall.

    • Walked upright.

    • Small brain volume (~530 cm^3) versus modern humans (~1,450 cm^3).

• Genus Homo

  • Emerged about 2.5 million years ago, lasting until 1.8 million years ago.

  • Includes species:

    • Homo habilis

    • Homo ergaster

    • Homo erectus

  • Generally taller and had larger brains compared to Australopithecus.

  • Utilized stone tools and transitioned to carnivorous diets.

Modern Human Evolutionary Timeline

• Approximately 300,000 years ago, Homo sapiens and Neanderthals emerged.

• Neanderthals eventually could not compete with Homo sapiens and became extinct.

Microorganisms

Domains of Life

1. Bacteria

2. Archaea

3. Eukarya

Bacteria

• Characteristics:

  • Single-celled, no nucleus, single loop of DNA, cell wall with peptidoglycan.

  • Shapes: spheres, rods, spirals.

Archaea

• Similar to Bacteria but with different cell membranes and no peptidoglycan.

• Many live in extreme environments (e.g., raw sewage, swamps, hot springs).

Eukarya

• Comprised of single-celled or multicellular organisms.

• Larger cell size compared to bacteria and archaea, with a nucleus and true chromosomes.

• Membranes consist of lipid bilayers, proteins, and cholesterol.

Structures and Functions of Bacteria

• General Structure:

  • Loop of DNA, cell wall, ribosomes (protein synthesis).

  • Hair-like structures (fimbriae) help in adhering to surfaces.

  • Sex pilus: hollow tube enabling DNA transfer between bacteria.

Additional Features

• Capsules: Outer protective layer, often present in disease-causing bacteria.

• Flagella: Whip-like structures aiding in bacterial movement.

Types of Bacteria

• Decomposers (Saprophytes): Break down dead organic matter.

• Commensal bacteria: Live on or in hosts, typically neutral.

  • Example: E. coli in the gut.

• Photosynthetic bacteria: Include cyanobacteria, perform photosynthesis like plants.

• Mutualistic bacteria: Benefit their host (e.g., gut bacteria producing antibiotics).

• Pathogenic bacteria: Cause disease and can grow in host tissues, producing harmful toxins (e.g., botulism).

Survival Mechanisms

• Some bacteria form endospores for survival in harsh environments, enabling them to withstand dry conditions for extended periods.

  • Upon moisture return, they germinate and grow, potentially leading to lethal infections.

Domain Eukarya

Kingdoms of Eukarya

• Protista

• Fungi

• Plantae

• Animaliae

Kingdom Protista

• Divided into three groups:

  • Algae

    • Various forms (single-celled to multicellular).

    • Contain chloroplasts for photosynthesis.

    • Typically found at the water's surface for sunlight access.

  • Protozoa

  • Fungi-like Protists

Algae Details

• Single-cell algae:

  • Diatoms: Brown algae with silicon dioxide in cell walls; sediment forms when they die.