Tracing Evolutionary History

Unit 6.1: Tracing Evolutionary History

• Early Earth was very hot due to the impact of meteorites and the compactness of gravity
• The Miller-Urey experiment tested if organic molecules could be created on early Earth; its findings support that life evolved on Earth spontaneously

Steps Necessary for Life

• Abiotic synthesis of organic molecules occurs
• Monomers join into polymers
• Polymers are packaged into protocells
• RNA self-replicates, leading to inheritance

History of Life on Earth

• The endosymbiotic hypothesis explains the generation of mitochondria and chloroplasts in the evolution of eukaryotic cells

Radiometric Dating

• Radiometric dating and the relative position of a fossil within rock strata help determine the age of rocks
• Radiometric dating is based on the decay of radioactive isotopes

Steps of Radiometric Dating

• List and practice the steps in the process of radiometric dating
• Interpret a half-life graph

Origin of Prokaryotes

• The earliest prokaryotes are stromatolites
• Prokaryotes were the sole inhabitants from 3.5 to 2 billion years ago
• Prokaryotic photosynthesis led to oxygen saturation of the seas, and appeared 2.7 billion years ago
• 2.2 billion years ago, O2 increased rapidly
• Most prokaryotes went extinct, but some lived in anaerobic environments
• Cellular respiration allowed other prokaryotes to survive

Origin of Single-Celled Eukaryotes

• Originating 1.8 billion years ago
• Small prokaryotic cells took up life inside larger cells
• Many unicellular forms evolved after they appeared

Origin of Multicellular Eukaryotes

• Algae, plants, fungi, and animals
• The first algae appeared 1.2 billion years ago
• Larger and more diverse organisms appeared 600 million years ago

Cambrian Explosion

• A period of time where the diversity of animals greatly increased

Colonization of Land

• Prokaryotes covered land a billion years ago
• Large forms of life appeared 500 million years ago
• Plants colonized in the company of fungi
• Most plants still have fungi in roots that aid in absorption of water and minerals
• Fungi receive nutrients in return
• Arthropods (insects) and tetrapods (vertebrates with 4 appendages) are the most widespread and diverse land animals

Elements and Isotopes

• Fossils contain isotopes of elements that accumulated when organisms were alive
• Once an organism dies, the isotope decays
• The rate of decay is considered the half-life
• Knowing the half-life of an isotope and the ratio to the stable isotope lets us determine the age of a fossil
• A longer half-life is used to date older fossils
• A lower half-life is used to date younger fossils

Unit 6.2: Bacteria and Protists - Prokaryotic Life

Diversity and Importance

• There are 10 times more prokaryotes than eukaryotes
• Metagenomics collects samples from specific environments and isolates/sequences DNA
• Microbiome computer software assembles collections of genomes of one species in a given environment
• Human microbiome: Trillions of microorganisms living on/within the body
• Impacts: digestion, immune function, metabolism, and mental well-being

Prokaryote External Features

• Shapes include cocci, bacilli, and spirochetes
  • Streptococci causes strep throat
  • Staphylococcus, which is a cluster

Cell Wall

• All prokaryotes live in a wide range of environments
• Cell walls provide physical protection and prevent bursting

Gram Staining

• Differentiates bacteria based on cell wall structure
• Gram-positive bacteria have simpler walls with a thick layer of peptidoglycan
• Gram-negative bacteria have less peptidoglycan and are more complex, containing an outer membrane with lipids

Projections

• External structures extend beyond the cell wall, such as flagella and fimbriae

Prokaryote Success Adaptations

• Endospores are developed when the environment is too harsh for a prokaryote to reproduce in the long run

Nutritional Diversity

• Photoautotrophs harness sunlight and use CO2 for carbon
• Photoheterotrophs obtain energy from sunlight but get carbon from organic sources
• Chemoautotrophs harvest energy from inorganic chemicals and use carbon from CO2 to make organic molecules
• Chemoheterotrophs acquire energy and carbon from organic molecules; the most diverse group of prokaryotes

Biofilms

• Consist of one or several species of prokaryotes, including protists and fungi forming highly organized colonies
• Common in bacteria that cause disease in humans like ear and urinary tract infections

Biofilm in Cystic Fibrosis

• Cystic fibrosis patients are vulnerable to pneumonia caused by biofilm-creating bacteria

Toxins

• Exotoxins are proteins secreted by bacterial cells into the environment and can cause major diseases when entering through a wound
• Endotoxins are lipid components of the outer membrane of gram-negative bacteria that are released when the cell dies, potentially causing septic shock

Addressing Human Needs

• Bioremediation uses organisms to remove pollutants from soil or water
• Useful for cleaning up toxic chemicals released into soil and water

Domains of Life: Differences in Cellular and Biochemical Traits

• Refer to Table 16.7 for differences between Bacteria, Archaea, and Eukarya

Archaea

• Extreme halophiles thrive in salty places
• Extreme thermophiles thrive in hot water

Bacterial Genetic Variation

• Transformation: The cell takes up DNA from the environment
• Transduction: Genes are transferred between bacteria and viruses
• Conjugation: Genes are directly transferred from one bacterium to another

Unit 6.3: Plants & Fungi

Plant vs Fungi

• Plants are autotrophic, making their own food through photosynthesis
• Fungi are heterotrophic, obtaining nutrients by absorbing organic matter

Challenges of Terrestrial Life

• Maintaining moisture
  • Aboveground parts of most land plants have a waxy cuticle which prevents water loss
• Obtaining resources from two locations
  • Adaptations: roots, stems, and leaves all aid in getting water/mineral nutrients in the soil or light/CO2 in the ground

Bryophytes

• Resemble other plants in having apical meristems and embryos that are retained on the parent plant, but lack true roots/leaves (ex: mat of moss)

Vascular Seedless Plants

• Have vascular tissue to transport water and nutrients but do not produce seeds (ex: ferns)

Gymnosperms

• Have "naked" seeds and are the earliest seed plants (ex: ornamental ginkgo tree)

Angiosperms

• Flowering plants that have complex reproductive structures that develop seeds within protective chambers (ex: flowering trees/shrubs)

Plant Life Cycle and Alternation of Generations

• Refer to the plant life cycle diagram for details on the alteration of generations

Parts of a Flower

• Sepals: Enclose the flower before it opens
• Petals: Attract animal pollinators
• Stamens: Produce pollen which house reproductive structure
• Anther: Contains male sporangia
• Carpels: female reproductive stricture
• Ovary: Angiosperm adaptation that encloses ovules
• Each ovule contains a sporangium that will produce a female gametophyte and will eventually become a seed

Fruits

• Ripened ovary of a flower is an adaptation to help disperse seeds

Monocots vs Dicots

• Refer to the diagram for differences between monocots and dicots

Fungi Characteristics

• Eukaryotic and heterotrophic

Economic Importance

• Beneficial fungi : truffles/cheeses are foods, and actinomycetes produces antibiotics
• Harmful fungi cause parasitism/pathogens

Symbiosis

• A close relationship between two or more different species of organisms
  • Lichens are symbiotic with fungal hyphae