What is Life?

Biology, Science, and How we Study Things.

What is Science

What is Life?

• Biology is the scientific study of life

• Define life by listing basic components– Cell is basic unit of life

– Every organism is one or more cells

– DNA used to produce proteins

Figure 1.1 Informational Molecule of Life.

Properties of Life

1. Organized

2. Uses energy

3. Maintains internal environment

4. Reproduces

5. Responds to the Environment

6. Grows, and develops

7. Evolves

Properties of Life

1) Order 2) Reproduction 3) Growth & Development

4) Energy Processing 5) Response to the Environment 6) Regulation

7) Evolutionary Adaptation

Properties of Life: Order

• Life has order and energy is required to maintain this order

1) Order

Properties of Life: Reproduction

• Life Reproduces Itself, Grows, and Develops

– Asexual reproduction

• All offspring identical

– Sexual reproduction

• Offspring have new combination of traits

– Growth and development

Figure 1.5 Asexual and Sexual Reproduction.

Properties of Life: Reproduction

Properties of Life: Growth and Development

• Grow and Develop – cell division and specialization until maturity

Properties of Life: Energy

• Every living thing needs energy to live– Metabolism – sum of the chemical reactions in an

organisms that produce and use energy

• Living things classified by how get energy– Producers – Autotrophs, make own food from nutrients

and non-living sources (sun)– Consumer – Heterotroph, get energy by consuming other

organisms (dead or alive)– Decomposer – Heterotroph, get energy from dead

organisms or wastes

• All types of organisms live together in ecosystem and make a food web

Properties of Life: Energy

ProducerConsumer

Decomposer

Simple Food Web

Producers extract energyand nutrients from thenonliving environment

Consumers obtainenergy and nutrients byeating other organisms.

Decomposers are consumersthat obtain nutrients from deadorganisms and organic wastes.

Properties of Life: Energy

Properties of Life Energy

Properties of Life: Respond to Environment

• Life can sense and react to stimuli

• To do this, cells have to be in constant environment (relatively!)

Properties of Life: Regulation/Homeostasis

• Homeostasis – Process by which cell or organisms maintains a state of internal constancy or EQUILIBRIUM

• Ex. Your internal temperature is 37⁰C or 98.6⁰F

Properties of Life/Adaptation

• How life changes over time to become best suited to its environment– Adaptation – Inherited trait that make organisms

better suited to environment • Better survival

• More successful reproduction

– Natural Selection – Through adaptation, a set of traits that make one organism more successful than another• Enhanced reproductive success leading to more

individuals

Properties of Life/Adaptation

Properties of Life: Natural Selection in Bacteria

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

a. b.SEM (false color) 10 µm

Staphylococcus aureus

before mutation

Generation1 Generation2 Multiple generations later

Antibiotic-resistant bacteria

are most successful

Mutation

occurs (red)

Time

Antibiotic present

Time

Reproduction

and

Selection

a (left): © Dennis Kunkel Microscopy, Inc.; a (inset): © Ron Occalea/ The Medical File/Peter Arnold/Photolibrary

Hair

Bacterial

cell

Properties of Life: Natural Selection in Bacteria

Life is Organized

• Atoms• Molecules• Organelles• Cells• Tissues• Organs• Organ Systems• Organisms• Population • Community• Ecosystem• Biosphere

• Emergent Properties– Interacting properties that

give an organisms a complex function

– Change the structure, change the function

– Interrupt the function too much, structure breaks down

ATOM: The smallest chemical unit of a type of pure substance (element).Example: Lithium atom

MOLECULE: A group of joined atoms.Example: DNA

ORGANELLE: A membrane-bounded structure that has a specific function within a cell.Example: Chloroplast

CELL: The fundamental unit of life. Example: Leaf cell

TISSUE: A collection of specialized cells that function in a coordinated fashion.Example: Epidermis of leaf

ORGAN: A structure consisting of tissues organized to interact and carry out specific functions.Example: Leaf

COMMUNITY: All populations that occupy the same region.Example: All populations in a savanna

ECOSYSTEM: The living and nonliving components of an area.Example: The savanna

BIOSPHERE: The global ecosystem; the parts of the planet and its atmosphere where life is possible.

ORGANISM: A single living individual.Example: One tree

ORGAN SYSTEM: Organs connected physically or chemically that function together.Example: Aboveground part of a plant

POPULATION: A group of the same species of organism living in the same place and time.Example: Multiple acacia trees

Organization of Life

Tree of Life - Bacteria

• Cells lack nuclei (prokaryotic)• Unicellular

DOMAIN BACTERIA

Tree of Life ArchaeaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• Cells lack nuclei (prokaryotic)• Unicellular

DOMAIN ARCHAEA

Tree of Life Eukarya

• Cells contain nuclei (eukaryotic)• Unicellular or multicellular

DOMAIN EUKARYA

Kingdom Animalia

• Multicellular• Heterotrophs (by ingestion)

LM 200 µm

Kingdom Fungi Kingdom Plantae

• Most are multicellular• Heterotrophs (by external

digestion)

• Multicellular• Autotrophs

Protista (multiple kingdoms)

• Unicellular or multicellular• Autotrophs or heterotrophs

Scientific Method

• Sir Frances Bacon: the 1st to document the scientific method

Scientific Method

Experimental Design

• Used to test hypotheses– Can be controlled (in a lab) or in the natural environment

• What you need to consider– Sample size – How many individuals or observations do

you have to make– Variables – What can change in your experiment

• Independent Variable – The thing you change• Dependent Variable – The response• Standardized Variable – Constant

– Control – Provides basis for comparison– Statistical Analysis – Math using your data to prove or or

disprove your hypotheses

Sample Experiment

Observations –Fish community looks different when you change the shoreline

Hypothesis – A change in shoreline structure will change the fish community

Data Collection –Seine sampling to collect fish at sites

Sample Size –Measure 10 fish per species, total count, total biomass of all fish in each haul

Control –Control Sites –those with no change in shorelineImpact Sites – those with shoreline change

Data Analysis –Metrics (diversity, species richness, biomass), Statistical analysis

Theory – Based on data, the fish community is different at control sites than impact sites

Case Study on the Scientific Method

Question: Why do baby coots have ornamental plumage during the first three weeks of life?

Hypothesis: Bright ornamental plumage makes the chicks more attractive to the parents and increases survival

Prediction: If the hypothesis is supported, then removing the ornamental plumage will decrease survival (and body weight) of the chicks.

Case Study on the Scientific Method

Experimental Design: removed colorful plumage

None trimmed (control) All trimmed (control)

½ trimmed (experimental)

Case Study on the Scientific Method

Data: Measured weight and survival of the chicks

CONCLUSIONS?

Basic vs. Applied Science

• Basic: “pure science,” gain knowledge

• Applied: “technology,” solve real-world problems