Copyright © 2006 Cynthia Garrard publishing under Canyon Design Welcome to Biological Principles

Copyright © 2006 Cynthia Garrard publishing under Canyon Design

Welcome to Biological Principles


Chapter 1

What is biology about?


1) What is biology and “life” ?

2) How is life organized ?

3) How are biological systems related ?

4) How is so much diverse life classified ?

5) How did all these diverse life forms evolve ?

6) How do biologist study life ?


Question 1: What is Biology?

• What is Biology?

– Biology is the scientific study of life

• What do we mean by “life” ?

– How is life defined?


• We recognize life by the 7 things living organisms do:

1) Order – life is structured

2) Evolve – organisms evolve due to their environments

3) Respond to the environment – organisms change as their surroundings change

Fig 1.2


4) Regulate – organisms must maintain consistent internal balance regardless of external factors

5) Process energy – organisms must harvest energy to do work

6) Grow and develop – organisms get larger and mature over time

7) Reproduce – organism produce offspring

Fig 1.2


Question 2: How is all this “life” organized?

• Concept 1.1: Biologists explore life from the microscopic to the global scale

• The study of life

– Extends from the microscope scale of molecules and cells to the global scale of the entire living planet

– This is called the hierarchy of life


A Hierarchy of Biological Organization

• The hierarchy of life

1) The biosphere – all the environments on Earth that are inhabitable by life

2) Ecosystems – all the living things in a particular area & the non-living things that interact with life

3) Communities – all the living things in an ecosystem

4) Population – all the individuals of a species within a community

Fig 1.3



5) Organisms – individual members of a population

6) Organ systems and organs – team of organs that function together (organs are body parts made up of more than one type of tissue)

7) Tissue – a group of similar cells

8) Cell – fundamental unit of life; lowest level of hierarchy that retains all the characteristic of “life”

Fig 1.3



9) Organelle – functional component that make up a cell

10) Molecules – chemical structure consisting of two or more atoms

Fig 1.3


A Closer Look at Cells

• The cell

– Is the lowest level of organization that can perform all activities required for life

25 µmFigure 1.5


Two Main Forms of Cells

• All cells share certain characteristics

– They are all enclosed by a membrane

– They all use DNA as genetic information

• There are two main forms of cells

– Eukaryotic

– Prokaryotic


•Prokaryotic cells

– Small

– Simple

– Older (evolutionarilary speaking)

– No membrane-bound organelles

– No true nucleus

• Ex: Bacteria

Figure 1.8


•Eukaryotic cells

– Large

– Complex

– Newer (evolutionarilary speaking)

– Membrane-bound organelles

– True nucleus

• Ex: White blood cell

Figure 1.8


• Actual size comparison

EUKARYOTIC CELL

Membrane

Cytoplasm

Organelles

Nucleus (contains DNA) 1 µm

PROKARYOTIC CELL

DNA

(no nucleus)Membrane

Figure 1.8


Question 3: How are biological systems related?

• The Emergent Properties of Systems

– New properties emerge with each step upward in the hierarchy of biological order

• Reductionism

– Involves reducing complex systems to simpler components that are more manageable to study


• Feedback Regulation in Biological Systems

– A kind of supply-and-demand economy of biological systems

– In feedback regulation - the output, or product, of a process regulates that very process


• In negative feedback

– An accumulation of an end product slows the process that produces that product

B

A

C

D

Enzyme 1

Enzyme 1

Enzyme 2

Enzyme 3

DD D D

D

D

DD

DD

C

B

A Negative feedback

Figure 1.11


• In positive feedback

– The end product speeds up production

WW

X

Y

Z

ZZ

ZZ

Z

Z Z Z

Z Z Z Z

Z

ZZ Z

ZZ

Y

X

Enzyme 4

Enzyme 5

Enzyme 6

Enzyme 4

Enzyme 5

Enzyme 6

Positivefeedback

Figure 1.12


Question 4: How is so much diverse life classified?

• With all the diverse life forms, how can biologists classify them all?

Figure 1.13


Grouping Species: The Basic Idea

• Taxonomy

– Is the branch of biology that names and classifies species according to a system of broader and broader groups


• Classifying lifeSpecies Genus Family Order Class Phylum Kingdom Domain

Mammalia

Ursusameri-canus(Americanblack bear)

Ursus

Ursidae

Carnivora

Chordata

Animalia

EukaryaFigure 1.14


The Three Domains of Life

• At the highest level, life is classified into three domains

– Bacteria

• Ex: E.coli, staph, strep

– Archaea

• Ex: Pyrococcus furiosus

– Eukarya

• Ex: Us!


•Domain Bacteria

– Consists of prokaryotes

– All the bacteria you can think of

•Domain Archaea

– Consist of prokaryotes

– Live in extreme environments (high heat or salt concentration)

– “Junk drawer” of classification


• Domain Eukarya,

– Consist of eukaryotes

– Divided into several kingdoms:

• Protist (multiple kingdoms, usually unicelular)

• Plantae – plants

• Animalia – animals

• Fungi – decomposers (mushrooms)


Unity in the Diversity of Life

• As diverse as life is

– There is also evidence of remarkable unity at the cellular and molecular level Cilia of Paramecium.

The cilia of Parameciumpropel the cell throughpond water.

Cross section of cilium, as viewedwith an electron microscope

15 µm

1.0 µm

5 µm

Cilia of windpipe cells. The cells that line the human windpipe are equipped with cilia that help keep the lungs clean by moving a film of debris-trapping mucus upward.Figure 1.16


Just as the earth has changed over billions of

years,

species of living organisms have evolved

too


Question 5: How did diverse life forms evolve?

• The evolutionary view of life

– Came into sharp focus in 1859 when Charles Darwin published On the Origin of Species by Natural Selection

– His two main points were:

1) Contemporary species arose from a succession of ancestors

2) The evolutionary mechanism of natural selection accounts for descent with modification

Figure 1.18


• The study of fossils

– Helped to lay the groundwork for Darwin’s ideas

• Fossils are remains or traces of organisms from the past

– Usually found in sedimentary rock, which appears in layers or strata

Figure 22.3


• Paleontology, the study of fossils

– Was largely developed by French scientist Georges Cuvier

• Cuvier opposed the idea of gradual evolutionary change

– And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe


Theories of Gradualism

• Gradualism

– Is the idea that profound change can take place through the cumulative effect of slow but continuous processes


Lamarck’s Theory of Evolution

• Jean-Baptiste de Lamarck (1744 – 1829) hypothesized that species evolve

– Through use and disuse and the inheritance of acquired traits

– But the mechanisms he proposed are unsupported by evidence

Figure 22.4


• In 1844, Darwin wrote a long essay on the origin of species and natural selection

– But he was reluctant to introduce his theory publicly, anticipating the uproar it would cause

• In June 1858 Darwin received a manuscript from Alfred Russell Wallace

– Who had developed a theory of natural selection similar to Darwin’s

• Darwin quickly finished The Origin of Species

– And published it the next year


• Darwin’s ideas weren’t new, just connected for the first time.

• He saw:

1) Individuals vary in many traits

2) Individuals can produce more offspring than can survive, so they compete for resources


• From these observations Darwin inferred:

1) Not all individuals are equally likely to survive and reproduce

2) This unequal reproductive success can adapt a population to its environment


•The products of natural selection

– Often times seem to be “perfect” adaptations of organisms to the special circumstances of their way of life and their environment


• The Origin of Species articulated two main points

– Descent with modification

– Natural selection

Figure 1.19


• Natural selection is the evolutionary process that occurs

– When a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others

1 Populations with varied inherited traits

2 Elimination of individuals with certain traits.

3 Reproduction of survivors.

4 Increasing frequency of traits that enhance survival and reproductive success. Figure 1.21


Question 6: How do biologists study life?

• Biology blends two main processes of scientific inquiry

– Discovery science – describes nature

– Hypothesis-based science – explains nature


Discovery Science

• Discovery science

– Describes natural structures and processes as accurately as possible through careful observation and analysis of data


Induction in Discovery Science

• In inductive reasoning

– Scientists derive generalizations based on a large number of specific observations

Example: I’ve noticed that every time I throw a ball up, it comes back down, so I guess that the next time I throw a ball up, it’ll come back down too.

• Start with many observations, see a pattern, create a tentative hypothesis that may lead to a theory


Hypothesis-Based Science

• In science, inquiry that asks specific questions

– Tries to explain generalizations and seeks the causes of events observed

– Possible explanations are put on trial to see if they are falsifiable or not

• In science, a hypothesis

– Is a tentative answer to a well-framed question, an explanation on trial

– Makes predictions that can be tested


Hypothesis-Based Science

• Uses Deductive Reasoning

• In deductive reasoning

– Uses “If . . . Then” logic that starts with a general observation and flows to a specific result

– Example: If Newton’s Law of Gravity is true, and I throw a ball up, then it must come down

– Start with a theory that we then narrow to a hypothesis that is testable, narrow it further through observations that may or may not confirm the original hypothesis


A Closer Look at Hypotheses in Scientific Inquiry

• A scientific hypothesis must have two important qualities

– It must be testable – have to be able to check if the idea is valid

• Example: I can toss the ball up in the air

– It must be falsifiable – there must be some observation that could reveal if the idea was not true

• Example: If I observe the ball did not fall back down


A Closer Look at Hypotheses in Scientific Inquiry

• Hypothesis (continued)

– Isn’t ever “proven true”, it just hasn’t been falsified yet

– Tested in controlled experiments where two groups are compared:

1) Experimental group

2) Control group

Only differ in 1 factor, the factor that is being tested


Theories in Science

• A “theory” in science is different than in everyday usage of that word

• A scientific theory

– Is broad in scope

– Generates new hypotheses

– Is supported by a large body of evidence

Yet it isn’t “proven true”, just the best answer that fits the available data at the present

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Copyright © 2006 Cynthia Garrard publishing under Canyon Design Welcome to Biological Principles