Biology - Section 1: Evolution, the Themes of Biology, and Scientific Inquiry

Properties of Life

1. Order

2. Evolutionary Adaptation

3. Regulation

4. Reproduction

5. Response to the Environment

6. Growth and development

7. Energy processing

Themes of Biology

1. Organization

2. Genetic Information

3. Energy and Matter

4. Interactions

5. Evolution

Biological Organization: Biosphere

• All places on Earth where life exists

• All life on earth

Biological Organization: Ecosystems

• All living organisms in one area

• Co-exist with non-living components

Biological Organization: Communities

• Array of organisms inhabiting a particular ecosystem

Biological Organization: Populations

• All individuals of a species within a community

Biological Organization: Organisms

• Individuals within a population

Biological Organization: Organs

• Within body of an organism, made of multiple tissues

• Carry out specific functions of organism

Biological Organization: Tissues

• Groups of cells within an organ, working together

• Perform specialized tasks

Biological Organization: Cells

• Fundamental unit of structure and function

Biological Organization: Organelles

• Structures within cells that carry out specific functions

Biological Organization: Molecules

• Chemical structures composed of two or more atoms

Biological Organization: Reductionism

Reducing complex systems to simpler manageable units

• Example: studying the molecular structure of DNA

• Incomplete view of life

Emergent properties

Novel properties that emerge at each higher level of organization

• Due to arrangement and interactions of parts as complexity increases

• Example: Photosynthesis occurs in chloroplast but not chlorophyll and the other molecules in a test tube

• Difficult to study

Systems biology

System: network of independent components that function together

Systems biology models dynamic behaviour of biological system by studying interactions among system’s parts

• Can be used to study biology at all levels

• Examples: blood pressure global warming 14

Biological Organization: Structure and function

Structure and function are correlated at all levels of biological organization

• Leaves

• Thin, flat structure maximizes chloroplasts’ ability to capture sunlight

• Hummingbird wings rotate at shoulder, enabling hovering

• Ecosystem function results from interactions among biotic and abiotic components

• Nutrient cycling – N in atmosphere converted by plants to a form usable by animals

Cell theory

All living organisms are made of cells

All cells share which characteristics?

• Enclosed in membrane

• DNA as genetic information

Eukaryotic vs Prokaryotic Cells

Eukaryotic cells

• Membrane-enclosed nucleus

• Membrane-enclosed organelles

• Found in Eukarya

Prokaryotic cells

• Smaller and simpler

• No membrane-enclosed nucleus

• Found in Bacteria and Archaea

Genes

units of inheritance

• Encode information to build the molecules in cell

• Transmitted from parent to offspring

• Transmitted during each cell division within an organism

• Directs development of organism

Molecular Structure of deoxyribonucleic acid (DNA)

Two long strands arranged in a double helix

• Nucleotides

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Thymine (T)

Specific sequences of nucleotides make up genes

• Structure accounts for ability to store information

Gene expression

Process by which information in a gene controls production of a cellular product (protein).

• Intermediary – ribonucleic acid or RNA

• The gene is a section of DNA within a chromosome with a specific, unique sequence

Transcription

DNA sequence is copied to messenger RNA (mRNA)

Translation

mRNA sequence is translated to amino acid sequence

• Amino acid sequence determines protein produced

• A universal genetic code determines how the RNA sequence is translated to amino acids

• For some genes, RNA itself is the end product

Genome

Entire set of genetic material in organism

Genomics - study of whole genomes of one or more species

Proteome

All proteins expressed within given cell, tissue, or organism

Proteomics - study of sets of proteins and their properties

Large-Scale Analysis of Biological Sequences - Three research developments:

1. High-throughput technology

• Multiple samples analyzed simultaneously

• Rapid collection of large amount of data

2. Bioinformatics

• Using computational tools to analyze, store, and organize biological information

• DNA, RNA, protein sequences

3. Interdisciplinary research teams

Transfer and Transformation of Energy and Matter

Sunlight captured by producers is converted to chemical energy for themselves and for consumers

• Living organisms require energy to do work – for movement, growth, reproduction, cellular activities

• Energy input and transformation from one form to another makes life possible

Energy Flow and Chemical Recycling

Chemicals are recycled within an ecosystem ... decomposers

• Energy flows through ecosystem in one direction → light to heat

Feedback regulation

Allows biological processes to self-regulation. Product regulates process.

Negative feedback

• Response reduces/counteracts initial stimulus, returning a system to a balanced state

• Ex: Insulin signaling

Positive feedback

• Response reinforces stimulus, increasing response

• Ex: Platelets and injury

Interactions with Other Organisms and the Physical Environment

Organism interact continuously with physical features of environment

• Interactions regulate ecosystems as a whole

Organism - Organism interactions

• Mutually beneficial

• Parasitic (1 beneficial, 1 harmful)

• Mutually harmful

• Commensal (one species benefits, the commensal, while the other, the host, neither benefits nor is harmed).

Human Interactions with Environment

• Increased burning of fossil fuels last 150 years

• Excess CO2 release leading to trapped heat and global warming – 1oC since 1900

• Climate change – directional change to global climate lasting 30 years or more

• Consequences: loss of habitat, range shifts, population declines or species extinction, population increases

Examples:

• Increased mortality of polar bears

• Ivory gull population decline by 80%

• Mountain pine beetle outbreaks

Evolution

All living organisms are modified descendants of common ancestors.

→ Descent with modification

→ Explains both the unity and diversity of life

→ Accounts for adaptations of organisms to particular environments

Each species given two-part name:

✗ Genus – plural general

✗ Specific epithet – unique to species

✗ Example: Homo sapiens

The Three Domains of Life

• Bacteria (prokaryotes)

• Archaea (prokaryotes)

• Eukarya (eukaryotes)

Domains Bacteria and Archaea

• Prokaryotes are single-celled and microscopic

• Cell structure simpler than eukaryotes

Kingdoms of Eukarya

Four Kingdoms:

• Plantae - Photosynthesis

• Fungi - Absorb nutrients

• Animalia - Ingest other organisms

• Protists – Diverse group of single-celled eukaryotes

How can we account for life’s dual nature of unity and diversity?

Process of evolution accounts for life’s similarities and differences

• DNA as the universal genetic language

• Cell structures similar among diverse organisms

• Similar skeletons among vertebrates

History of life as documented by fossils and other evidence

Charles Darwin - Descent with Modification

Contemporary species arose from a succession of ancestors that differed from them.

Explains duality of unity and diversity

• Unity due to descent from common ancestor

• Diversity due to subsequent modifications in diverged lineages

Charles Darwin - Natural Selection

The cause of descent with modification.

✘ Individuals with inherited traits better suited to environment more likely to survive and reproduce

✘ Over generations, a higher and higher proportion of the population will consist of individuals with advantageous traits

✘ Evolution occurs as as unequal reproductive success leads to adaptation to the environment

Evolutionary Adaptation

The environment “naturally selects” individuals with advantageous traits for propagation

Result – adaptation of populations and species to local environment

The Tree of Life - Explanation

Over time ancestral species to give rise to 2 or more descendent species.

• Similarity due to common ancestor

• Diversity due to modification by natural section

• Example: Bat wing is modified forearm adapted for flight

• Common architecture with other mammalian forearms

The Tree of Life - Diagram

• Evolutionary relationships illustrated with tree-like diagrams

• Branch point represents common ancestors

• Closely-related species have more recent common ancestor and share more features

• Shows temporal dimension of biology

Gathering and Testing Data

✘ Observation – the gathering of information

✘ Data – recorded observations

• Qualitative

• Quantitative

✘ Statistics – branch of mathematics used analyze and determine significance of data

✘ Inductive reasoning – logic in which generalizations are based on many specific observations

✘ Scientific literature – set of published studies or findings

Forming and Testing Hypotheses

✘ Hypothesis – explanation, based on observations and assumptions, that leads to a testable prediction

• Guided by inductive reasoning

✘ Experiment – scientific test carried out under controlled conditions

✘ Scientific method – idealized process of inquiry based on hypothesis testing

✘ Limitations: not all hypotheses can be tested, or meet criteria of science

Deductive reasoning (if hypothesis is not proven correct)

logic in which specific results are predicted from a general premise.

✘ Hypotheses are not proven correct

✘ A hypothesis is supported when not proven incorrect

✘ Repeated testing increases confidence in validity

✘ Scientific consensus – shared conclusion that a particular hypothesis explains the known data and stands up to experimental testing

Variables

Factors being manipulated and measured

✘ Independent variable – factor being manipulated, values set by researcher

✘ Dependent variable – factor being measured, predicted to be affected by independent variable

Controlled experiment – experiment where an experimental group is compared to a control group

• Control group cancels effect of other features of the experimental environment

Theory

Explanation of aspect of natural world

• Broader than a hypothesis

• Generate new hypotheses

• Supported by large body of evidence

• May be modified or rejected upon new information