Great Ideas in Science Lecture 10 - Living Things Prof. Robert Hazen PROV-301

Every Living thing… Can be classified in one scheme Is modular – composed of a few simple molecules Is made of cells – life’s chemical factories Uses the same genetic code Evolved from a first cell by natural selection Lives in ecosystems of many interdependent organisms

Ways of Thinking About Living Things Biosphere Ecosystem Community Population Organism Anatomy & physiology Cellular Molecular

What is Life? Encapsulation: All life is separated from the environment by a membrane. Metabolism: All life obtains energy and atoms from the environment. Reproduction: All life reproduces via genetics.

The Characteristics of Life Life has a high degree of order & complexity. Life is part of larger systems of matter & energy. Life depends on chemical reactions in cells. Life requires liquid water. Organisms grow and develop. Organisms carefully control their use of energy. All life shares the same genetic code, which can be passed from parent to offspring.

Great Idea: Living things use many different strategies to deal with the problems of acquiring and using matter and energy. Linnaean classification Hierarchy Kingdom Phylum Class Order Family Genus Species

Why is Taxonomy Important? Think about how to describe a tree. Names are essential for accurate communications But taxonomy can be rather arbitrary Lumpers versus splitters Local variations in species

Why is Taxonomy Important? Dracorex (top left) and Stygimoloch (top right), as growth stages of Pachycephalosaurus (bottom).

Why is Taxonomy Important? C A B

Classifying Life Kingdoms Monera Protista Fungi Plants Animals

Taxonomy of Animals

Classifying Human Beings Kingdom: Animals Phylum: Chordates Subphylum: vertebrates Class: Mammals Order: Primates Family: Hominid Genus: Homo Species: sapiens Homo sapiens is the only surviving member of the Hominid family

A New View: Three Domains of Life Bacteria Archaea Eukarya

Implications of Linnaean Classification You can use genetic material to classify. Similarities depend on time and change. Classification results from real events. “Nothing in biology makes sense except in the light of evolution.”

Vascular Plants Phylum of vascular plants: They have roots, stems, and leaves that control water movements. Strategies Seedless plants (Ferns: spores are fertilized eggs) Seeds but no flowers (Gymnosperms: cones hold egg or sperm) Seeds and flowers (Angiosperms: The seed is an egg plus nutrients, while pollen is sperm)

Invertebrates These diverse animals have no backbone. Arthropods include 70% of known animal species. Their structures include an exoskeleton and jointed legs

The Molecules of Life All life is modular – composed of a few simple molecules.

Four key Ideas about the molecules of life Life’s molecules are based on Carbon (the topic of organic chemistry). Six main elements (CHNOPS) are dominant. Biomolecules are modular; they are built by arranging lots of smaller molecules. Molecular shapes determine their function.

Nutrition Facts Energy Lipids Sugars Amino acids

Carbohydrates (sugars) Carbon Hydrogen Oxygen

Cellulose and Starch

Cellulose and Starch

Lipids

Saturated and Unsaturated Lipids

Amino Acids Amino group Carboxyl group Side-group (20 different things)

Protein – sequence of amino acids Primary – chain of amino acids Secondary – folding of chain Tertiary Quaternary

Proteins Some play a structural role, as in hair, fingernails, spider webs, tendons, muscle fibers, and in bones.

Proteins Act As Enzymes

Dietary Amino Acids