Intro Notes: Themes in the Study of Life AP Biology Intro Notes: Themes in the Study of Life

Life’s Hierarchical Order Each level of biological structure builds on the level below it Atomscomplex biological molecules subcellular organellescellstissues organsorgan systems

Levels of Organization Organism Individual living thing Bison Tissues, organs, and organ systems Groups of Cells Nervous tissue Brain Nervous system Smallest functional unit of life Cells Nerve cell Groups of atoms; smallest unit of most chemical compounds Molecules Water DNA

Organism in a

There are levels of organization beyond the individual organism: Population-localized group of organisms belonging to the same species Community- populations of species living in the same area Ecosystem-energy processing system of community interactions that include the abiotic factors in the environment

Biomes- large scale communities classified by predominant vegetation type and distinctive combinations of plants and animals Biosphere- the sum of all the planet’s ecosystems

Levels of Organization, cont. Biosphere The part of Earth that contains all ecosystems Biosphere Ecosystem Community and its nonliving surroundings Hawk, snake, bison, prairie dog, grass, stream, rocks, air Community Populations that live together in a defined area Hawk, snake, bison, prairie dog, grass Population Group of organisms of one type that live in the same area Bison herd

Emergent properties (pg. 5) Each level of biological organization has emergent properties These are properties that emerge as a result of interactions between components

Some emergent properties and processes associated with life are the following: Order-organisms are highly ordered. Characteristics of life emerge from this complex organization. Reproduction- organisms reproduce their own kind; Life comes only from life (biogenesis)

Growth and development-Inherited information in DNA directs species- specific patterns of growth and development Energy Utilization-Organisms take in energy and transform it to do work, including maintaining their ordered state Response to the environment- Organisms respond to environmental stimuli

Homeostasis- Regulatory mechanisms maintain an organism’s internal environment within tolerable limits, even though the external surroundings may change. Evolutionary adaptations- Life evolves as a result of the interaction between organisms and their environments.

Cells are an organism’s basic unit of structure and function All organisms are composed of cells Cells exist as unicellular organisms, or as subunits of multicellular organisms Cells are the lowest level of structure capable of performing all life activities.

Based on structural organization, there are two kinds of cells: prokaryotes and eukaryotes Lack membrane-bound organelles and nucleus Found only in archaebacteria and bacteria Generally smaller than eukaryotic cells Almost all have tough external walls

Eukaryotes: Found in protists, plants, fungi, and animals Subdivided by internal membranes, forming organelles Contains DNA separated from the rest of the cell; organized into chromosomes found in the nucleus Plant cells have a cell wall; animal cells do not.

The continuity of life is based on inheritable information in the form of DNA Biological instructions for an organism’s complex structure and function are coded in DNA Each DNA molecule is made of 4 nucleotides: adenine, thymine, guanine, and cytosine The linear sequence of these 4 nucleotides encode the information in a gene

Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Inheritance Inheritance is based on a complex mechanism for copying DNA and passing the information on to offspring. All forms of life use essentially the same genetic code. Differences among organisms reflect differences in nucleotide sequence.

Structure and function are correlated at all levels of biological organization. There is a relationship between an organism’s structure and how it works. Knowing a structure’s function gives insight about its construction. Example: aerodynamic design of a bird’s wing, internal bone structure, and muscle arrangement suitable for flight

Ecosystem dynamics include nutrient cycling and energy flow (Fig. 1.7) Organisms are open systems that interact continually with their environment Both the organism and the environment are affected by this interaction. Ecosystem dynamics include nutrient cycling and energy flow (Fig. 1.7)

Regulatory mechanisms ensure a dynamic balance in living systems Many biological processes are self-regulating (feedback regulation) Positive feedback speeds a process up Negative feedback slows a process down

Examples of Feedback Inhibition Thermostat senses temperature change and switches off heating system Heating system turns on Room temperature decreases Thermostat senses temperature change and switches on heating system

Evolution, Unity, and Diversity Biological diversity is enormous. Estimates range from 5 million to over 30 million species. About 1.5 million species have been identified and named, including approximately 260,000 plants, 50,000 vertebrates, and 750,000 insects.

Taxonomy Taxonomy is the branch of biology concerned with naming and classifying organisms. Taxonomic groups are ranked in a hierarchy from the most to least inclusive category: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species

Five Kingdoms (traditional classification) Monera- prokaryotic organisms (Bacteria) Protista- unicellular eukaryotes Plantae-plants, photosynthetic organisms Fungi-fungi, eukaryotic decomposers Animalia- animals, most obtain food by ingestion

Unity There is unity in the diversity of life forms at the lower levels of organization. Unity of life forms is evident in a universal genetic code, similar metabolic pathways, and similarities of cell structure.

Evolution is the core theme of Biology Life evolves as species change over time. Species that are very similar share a common ancestor at a recent branch point on the phylogenetic tree. Less closely related organisms share a more ancient common ancestor. Natural selection is the mechanism of evolutionary change (survival of the fittest)

Science as a Process Testable hypotheses are the hallmarks of the scientific process Scientific method is the process which outlines a series of steps used to answer questions. (Controlled experiments) Science is based on the conviction that natural phenomena have natural causes. Evidence is required to solve problems

Scientific Hypotheses Are possible explanations Reflect past experience Multiple hypotheses should be proposed whenever possible Hypotheses must be testable using the hypothetico-deductive approach Hypotheses can be eliminated but not confirmed with absolute certainty

Reznick and Elder research

Showed that selective predation resulted in evolution over a short time period

Science and technology Science and technology are functions of society, and are interdependent. Technology extends our ability to observe and measure so that scientists can work on new questions. Science generates information to make technological inventions possible Technology has improved our standard of living, but not without environmental and ethical consequences.

Biology is a muliti-disciplinary adventure Biology integrates concepts from chemistry, physics, and mathematics, with influences from humanities and social sciences. As a science, biology is an ongoing process. New research methods and technologies have led to an “information explosion”