Properties of Life and Biological Organization

Properties of Life

• Living organisms share eight key characteristics or functions
• Order: Atoms -> Molecules -> Macromolecules (e.g., proteins, lipids, DNA, RNA, carbohydrates)
• Sensitivity or response to the environment: All living things respond to stimuli
• Reproduction: All living organisms reproduce to make new organisms
• Adaptation: Adjustments to their environment, which allow for survival
• Growth and development: Increase in size from birth, and or changes in form
• Regulation/homeostasis: Maintaining a stable internal environment
• Energy processing: Obtaining and using energy for life functions
• Evolution: Changes in genetic characteristics over time

Biological Levels of Organization

• Macromolecules build -> Organelles -> Cells -> Tissues -> Organs -> Organ Systems -> Organisms -> Populations -> Communities -> Ecosystems -> Biosphere.

• Organelles: Examples include the nucleus

• Cells: Examples include human blood cells

• Tissues: Examples include human skin tissue

• Organ Systems: Examples include the digestive system

• Organisms: Individual living things

• Populations: Groups of the same species

• Communities: Collection of different species in a given area

• Ecosystems: The interactions of communities with their environment

• Biosphere: All ecosystems on Earth

How Science Works

• Exploration and Discovery: Includes new technology, making observations, asking questions, serendipity, curiosity, exploring the literature, sharing data and ideas, finding inspiration.
• Gathering Data: Includes hypotheses, expected results/observations vs. actual observations, supporting, contradicting, surprising or inconclusive data, feedback and peer review, replication, coming up with new questions.
• Testing Ideas: Includes developing technology, addressing societal issues, building knowledge, informing policy, satisfying curiosity, solving everyday problems. Benefits and outcomes.
• Community Analysis and Feedback: Includes discussion with colleagues and publication.

Two Types of Reasoning

• Inductive Reasoning: Starts with observations and develops a general conclusion. Example: Observing members of a species are not identical and individuals compete for resources, leading to the conclusion that individuals most adapted to their environment are more likely to survive.
• Deductive Reasoning: Starts with a general idea and predicts specific outcomes. Example: If the average temperature in an ecosystem increases, individuals better adapted to warmer temperatures will outcompete those who are not.

Descriptive vs. Inferential Statistics

• Descriptive Statistics: Summarize observations from the real world.
• Inferential Statistics: Draws conclusions via inferences/inductions from observations in the real world to the real world laws

Phylogenetic Trees

• Rooted phylogenetic tree: An ancestral lineage gave rise to all organisms in the tree.
• Branch point: The place where two lineages diverged.
• Basal taxon: An early-evolved lineage that remains unbranched.
• Sister taxa: Two lineages that stem from the same branch point.
• Polytomy: A branch with more than two lineages stemming from a node.

Evolutionary Relationships (Vertebrates)

• A ladder-like tree, rooted by an organism with no vertebral column identifies branching points where characteristics are shared

Molecules (Hemoglobin)

• Molecules, including DNA, are composed of atoms
• Hemoglobin is a complex molecule, found in red blood cells
• Consists of a heme group, alpha and beta chains.

Water

• Polarity of water: Due to the differing electronegativities of hydrogen and oxygen, the slightly negative oxygen attracts the slightly positive hydrogens of another water molecule
• Hydrogen bonds: Attraction between the slightly negative oxygen on one molecule and slightly positive hydrogen of another water molecule

Nucleic Acids (DNA)

• DNA is a double helix structure
• Hydrogen bonds connect the DNA strands together.
• Nucleotides are the components of DNA, composed of nitrogenous base, a pentose sugar (deoxyribose), and one or more phosphate groups

Dehydration Reaction

• In dehydration synthesis reaction, two molecules of glucose are linked to form the disaccharide maltose
• Water molecule is formed as a byproduct

Hydrolysis Reaction

• The disaccharide maltose is broken down to form two glucose monomers with the addition of water.
• This reaction is the reverse of dehydration synthesis.

Amino Acids

• Amino acids have a central asymmetric carbon atom to which an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R group) are attached.
• There are 20 common amino acids found in proteins.

Peptide Bonds

• Peptide bond formation is a dehydration synthesis reaction
• The carboxyl group of one amino acid is linked to the amino group of another amino acid
• Water molecule is released

Protein Structure

• Primary structure: Amino acid sequence
• Secondary structure: x helix
• Tertiary structure: Tertiary structure is a three-dimensional structure, created by folding and interaction of parts of the primary structure
• Quaternary structure: Multiple polypeptide chains are folded to create a single protein, examples include hemoglobin

Central Dogma of Biology

• The central dogma is the flow of genetic information from DNA to RNA to protein
• DNA replication is the duplication of DNA, which allows genetic information to be passed to offspring.
• DNA transcription is the conversion of DNA's genetic information into messenger RNA
• RNA translation is the conversion of mRNA to proteins.

Transcription in Prokaryotes

• mRNA, a copy of the DNA protein-coding information, has the same base sequence as one strand of DNA.
• mRNA nucleotides base pairs with the DNA template strand, mRNA synthesis is 5' to 3'.
• mRNA is synthesized by RNA polymerase

mRNA Processing

• Pre-mRNA is processed to produce the final mRNA that leaves the nucleus.
• Introns are removed and exons are spliced together.
• A 5' cap and 3' poly-A tail are added to the mRNA.

Translation

• mRNA is translated into protein through a series of stages
• Ribosomes contain the mRNA and tRNAs.
• The mRNA codes for the sequence of amino acids that form a protein.

Evolution

• Evolution: change in the genetic composition of a population over time
• Evolution by natural selection occurs when heritable variations lead to differential reproductive success
• Natural selection acts on individuals but only populations evolve as organisms with useful, heritable variations tend to survive and reproduce.

Evidence of Evolution

• Similar anatomical structures in different organisms suggest common ancestry

Speciation

• Evolution leads to new species, evolution within a population is microevolution. The origin of new species = macroevolution
• Biological species concept: Reproductive isolation between populations.
• Morphospecies concept: Morphologically distinct populations.
• Phylogenetic species concept: Smallest monophyletic group on a phylogenetic tree.

Reproductive Isolation Mechanisms

• Prezygotic isolation: Prevents mating or blocks fertilization
• Temporal isolation: Species breed different times
• Habitat isolation: Species have different habitats
• Behavioral isolation: Species have different courtship rituals
• Mechanical isolation: Species have incompatible reproductive structures
• Gametic isolation: Eggs and sperm are incompatible
• Postzygotic isolation: Occurs after fertilization
• Hybrid viability: Offspring fail to develop or survive
• Hybrid sterility: Offspring are infertile
• Hybrid breakdown: First-generation hybrids fertile, but subsequent generations infertile

Polyploidy and Sympatric Speciation

• Polyploidy: Organisms have more than two sets of chromosomes (autopolyploidy or allopolyploidy)
• Polyploidy and sympatric speciation: A mechanism for the origin of new species, via hybridization

Natural Selection

• Stabilizing Selection: Favors the average phenotype
• Directional Selection: Favors one extreme phenotype
• Diversifying Selection: Favors both extreme phenotypes, selection against the average phenotype.

Explore the essential characteristics that define living organisms and the biological levels of organization. This quiz covers important concepts such as reproduction, adaptation, and energy processing, as well as how complex structures are formed from macromolecules to ecosystems. Test your knowledge of life sciences!