BY 101 CH 1-3. Exam 1

Chapter 1

Scientific Method and the Characteristics of Life

1.1, 1.2, 1.6, 1.8

Two main categories of science:Social and Natural. Natural sciences include: biology, physics, chemistry, astronomy, and Earth Sciences.

• Scientific method

  • Answers questions w/o bias

    • Make an observation

    • Form hypothesis

    • Design an experiment

    • Collect data

    • Interpret data to get results

    • Draw a conclusion

• Scientific theory

  • A hypothesis supported by a large body of observations and experiments

    • I.e Theory of evolution by natural selection, gravity, germ theory

      • Attempts to explain how phenomenon happens

• Scientific law

  • Phenomenon that always occurs under certain conditions

    • I.e law of gravity, law of thermodynamics, mendelian laws (genetics)

      • Doesn’t explain how phenomenon happens

Law explains what will happen, theory explains how

• Characteristics of life

  • Has cells

  • Maintain homeostasis

  • Uses energy/metabolizes

  • Reproduces

  • Growsandr develops

  • Adapts/evolves to environment

  • Responds to stimuli in environment

Reproduction is how organisms pass on genetic information, can be sexually (two parents combine genetic info), or asexually (one parent produces a clone).

Individuals adapt, populations evolve

Levels of Biological Organization

• Atoms

  • The smallest unit of a substance

• Molecules

  • Atoms bond to form molecules

• Cells

  • Smallest unit of Life, specialized function

• Tissues

  • Specific cells organized into specific patterns, special functions

• Organs

  • Structure made of tissues, carries out specific tasks

• Organ systems

  • Interacting organs to perform bodily funtions

• Organism

  • Organism made of cells

Not all organisms will have ALL levels or organization. Unicellular organisms won’t have organs, organ systems, etc. because they’re only a single cell.

• Population

  • All individuals of the same species in the same area

    • Species: group of organisms that can reproduce with each other and create fertile offspring

• Community

  • Different species populations interacting in the same area

• Ecosystem

  • Community interacting with environment

• Biosphere

  • Collection of ecosystems; anywhere life exists. Land, ocean, air.

Taxonomy: Naming and Classifying Organism

Common names for organisms are problematic. They can vary by location, be misleading, or the same common name can apply to many species. Taxonomy is the science of naming, describing, and classifying organisms; the father of this science is Carl von Linne.

• Scientific Names

  • Binomial Nomenclature “two names”

    • 1. Genus

    • 2. Specific epithet (species)

  • Organism are assigned to ranking based on:

    • Morphology- their traits

    • DNA- specifically genetic lineage, their relation to other organisms

The Rankings are as follows:

• Domain

  • Archaea

    • Smallest domain. Unicellular, similar to bacteria, found everywhere, crucial for human microbiome

  • Bacteria

    • Largest domain. Everywhere, many important functions, vast majority are harmless, a lot of them are actually beneficial

  • Eukarya

    • 2nd largest domain. Most organisms we think of. Plant, animals, fungi, and protists

• Kingdom

  • Eukarya

    • Animalia: sponges, dolphins, insects, frogs, etc.

    • Plantae: plants

    • Fungi

    • Protista: algae, slime molds, amoeba

  • Bacteria

    • Eubacteria: just bacteria

  • Archaea

    • Archaebacteria: just archaea

• Phylum

  • Plural: phyla

  • Examples: cordata, mollusca, arthropoda,

• Class

  • Examples: mammalia, aves, insecta

• Order

  • Examples: primates, coleoptera, rosales

• Family

  • Examples: hominidae, silphidae, rosaceae

• Genus

  • Plural: genera

  • Examples: canis, homo

• Species

  • Examples: coyotes, wolves, dogs

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Evolutionary History Of Life

Evolution is the basis of biology. Taxonomy is always evolving, there’s no “right way” to classify organisms; do you do it based only on traits, descent, or genetic makeup?

Bacteria were the first living organisms on Earth. Archaea appeared around the same time as bacteria, they’re primitive organisms- going by their distinct characteristics. Eukarya (aka eukaryotes) evolved a little over a billion years ago (BYA), their origin isn’t quite known, there’s theories though.

• Endosymbiotic Theory

  • Mitochondria and chloroplast in eukaryotic cells were once smaller bacteria that were ingested by a larger bacteria

When Bacteria and Archaea Dominated

• World was mostly bodies of water

• Very little oxygen in atmosphere (mostly sulfur, nitrogen, methane)

• Cyanobacteria start producing O₂ as waste from photosynthesis

• Oxygen is good for metabolism, organisms that can breathe begin to thrive; these organisms are out-competing bacteria

• Eukaryotes (they have a true nucleus) show up ~1 BYA and use O₂

• ~600 million years ago (MYA) multicellular eukaryotes evolve

Explosion of Diversity

• Animals ~543-490 MYA

• There’s land, organisms like the water though

• Decline in O₂ depleting bacteria; more O₂ for eukaryotes = explosions of animals (this is probably why, anyhow)

• The lineages of modern animals starts now

• Descendants of modern plants 443-417 MYA

Eukaryote Criteria

1. Cell compartmentalization

   1. Cell specialization in the form of membrane bound organelles

2. Multicellularity

   1. organisms can deal with their environments in novel ways and exploit new niches (cells, tissues, organs, organ systems).

3. Sexual Reproduction

   1. Allows for greater genetic diversity

Taxonomy Using Evolutionary Relationships

• Organisms in the same grouping = common ancestor b/c natural selection

• 3 ways to define these evolutionary relationships

  • Fossil Record: compare the old and modern species

  • Homologous Structures: similar physical features in organisms with a common ancestor, even if the features serve completely different functions

  • DNA: Genetic sequencing, similar DNA or no

Taxonomic ranking definitions can evolve too! Eukarya has been updated from 4 to 12 kingdoms; protista is no longer a kingdom but can be used as an umbrella term to reference the same organisms.

Source of Biodiversity: 5 Mass Extinctions

Mass Extinction - extinction of a large number of species in a short geologic time, usually caused by specific events. Open niches are left for remaining species to evolve into. 99% of species found in fossil records are extinct from mass extinctions. But the remaining 1% still has tons of diversity

• ~1.8 Million species have been described

  • Half of those are insects

    • 75% of which are beetles

  • Vertebrates are about 5%

    • They’re the best understood and described

  • New and old species are still being discovered and described estimated ~30 million species are out there