CHAPTER 1

Introduction: Biology Today

Today: Start Chapter 1: Introduction into the life sciences - Biology today • The subject of biology

• Definition of life • Fields of life sciences • The units, molecules, and diversity of life

Last time: • Why life sciences are relevant for engineers • Overview of course

Next time: • Overview of life forms • The unity in the diversity of life • The theory of evolution explains and connects unity and diversity • Evolution and engineering: Life versus machines

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• A strong scientific (minimalistic) definition of life does not yet exist

• So far, we recognize life largely by what living things do

• All life is unified by a common set of characteristics

• Life is not a thing but refers to a state of a system. So more precisely we should say something is ALIVE.

What is life?

The properties and processes that we associate with life

Reproduction

Order

Homeostasis

Conversion of energy and matter

Individual adaptation

(short-term)

Growth and development

Group adaptation (long-term)

The properties and processes that we associate with life

Reproduction

Order

Homeostasis

Conversion of energy and matter

Group adaptation (long-term)

All living things exhibit complex but ordered organization

Is the ability (by regulation) to keep the internal environment within limits that sustain life

Genes control the pattern of growth and development

•Organisms take in energy and transform it in all their activities

•Biosyntheses (Anabolism) and degradations (Catabolism)

Organisms reproduce their own kind

Capacity of populations to change (evolution)

Growth and development

Individual adaptation

(short-term)

Environment acts as source of signals that

trigger specific physiological responses

•Individual members of a species may not meet all the criteria, but are still considered alive.

Nice video: Life as an entropy-creating machine (9:48 min)

http://www.youtube.com/watch?v=csMPmxeEk2U&feature=player_embedded#!

•The thermodynamic approach to life:

•Disorder of an isolated system can only increase (Law of thermodynamics) •The quantitative measure of disorder is called entropy in physics •Life is a “machine” that increases total disorder of the organism + its environment. •So, life itself has a low entropy (high order) but the WHOLE system increases its entropy (increases its disorder)

Something to think about

• Must life be based on cells?

• Must life have the same chemical nature as our life?

• A thinking computer– would that be life?

• Is Earth alive?

•The Earth’s surface is in chemical disequilibrium

•Disequilibrium is stabilized by homeostasis

•The biosphere might reproduce spaceships seeding other planets

An overview of the field of biology

• Biology is the scientific study of life.

• A more modern name for biology is “life sciences” (“생물학”)

• Biologists explore several dimensions of the phenomenon of life

• Life is structured on a size scale ranging from the molecular to the biosphere.

• On many levels, there is an enormous diversity of life

• Since so many questions are asked in biology, there are many ways to categorize the life sciences

Life science disciplines focus on different aspects of life, such as

•Level of organization

•Category of organism

•Development of an organism

•History of life

•The physics of life

•The chemistry of life

•The information stored in life

•The regulatory mechanisms of life

•Dysfunctional life (disease)

•The uniquely important animal species Homo sapiens

Categories of the life sciences

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•Biochemistry •Molecular biology

•Ecology

•Cell biology

•Neurology •Cardiology

•Behavioral biology

•Genetics

•Earth physiology

•Biogeochemistry Focus on

• The level of organization Many disciplines

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Focus on

• Category of organism Zoology, mycology, botany, microbiology

Specific goal: description and categorization of life forms

Focus on

• Development of the individual Embryology, developmental biology

Specific goal: explain in detail how a single cell can convert into a complex organism

( the organism as a self-building machine)

Focus on

• History Evolutionary biology, palaeontology

Specific goal: trace and explain the origin of present biodiversity, including the origin of life and the origin of man

• Physics Biophysics • Chemistry Biochemistry • Regulation Biocybernetics

Focus on

Specific goals: explain in detail how the laws of physics, chemistry, and cybernetics are used by organisms

Focus on

• Information Bioinformatics

Specific goal: Organize and make easily accessible biological information

Focus on

• Function of cells and organs Physiology

Specific goal: provide an integrated explanation (including physics, chemistry, cybernetics) of cell and organ function

Focus on

• Disease pathology, pharmacology

Specific goal: explain the origin of disease and provide methods to fight it

Focus on

• Humans Anthropology

Specific goals: describe humans as an animal species (their evolution, physiology, etc; provide biological explanations for their sociology)

A quick overview of life in space

• The units of life

• The molecules of life

The units of life – 1. the cell

• The cell is the lowest level of structure that can perform all activities required for life.

– All organisms are composed of cells.

– The cell is the organism’s basic unit of structure and function

– Unicellular and multicellular organisms

– Cell’s dividing ability: basis for all reproduction, growth, and repair

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

• Prokaryotic cells) = bacteria

(small, contain no organelles).

• Eukaryotic cells (in plants, animals, fungi, and others)

(larger, more complex, contain organelles).

– Are subdivided by internal membranes into functional compartments or organelles

– The nucleus is the largest organelle in most eukaryotic cells.

We can distinguish two major types of cells

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The units of life – 2. the ecosystem • Each organism interacts continuously with

its environment. – Both organism and environment are

affected by the interactions.

• The biosphere contains multiple highly diverse ecosystems (desert, forest, deep sea, arctic, …)

• Humans so far don’t understand ecosystems well and largely ignore their complexity

• The dynamics of any ecosystem depend on two processes:

– Cycling of nutrients (recycle) – Flow of energy (one way: sunlight

→ producer → consumer)

• And which is the largest unit of life? – Not clear! – … perhaps the Earth itself? The Gaia hypothesis

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

• All cells use DNA as the chemical material of genes. – Genes are the units of inheritance that transmit

information from parents to offspring. • The language of DNA contains just four letters:

– A, G, C, T

“Molecules of life”

• The main kinds of molecules of life are: • Proteins • Sugars • Lipids • Nucleic acids (DNA, RNA)

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• Genetic engineering and biotechnology have allowed us to manipulate the DNA and genes of organisms: this is possible because biological information is written in the universal chemical language of DNA

Example: •The biological information (DNA) how to produce the human protein insulin was transferred into yeast

•Now yeast cells produce large quantities of insulin in bioreactors.

Life in Its Diverse Forms

• Diversity is the hallmark (상징, 대표적인 특징) of life.

– The diversity of known life includes 1.8 million species. (Plants 식물 290,000종, vertebrates 척추동물 52,000 종, insects 곤충 1,000,000 종을 포함하고 있음)

– Estimates of the total diversity range from 10 million to over 200 million

• Much of this diversity is presently only recognized molecularly (DNA sequencing)

•Outer appearance •Anatomy, embryology, ultrastructure

•Sequences of selected proteins or nucleic acids

•Sequences of genomes

1977 Carl Woese Sequence comparison of ribosomal RNA

Medieval times

2001 Craig Venter Sequencing of seawater microbes

1758 Carl von Linne Systema Naturae

How biological diversity is assessed

•This question has two sides:

•Which mechanisms lead to diversity? geological evolution drives the evolution •Why is diversity maintained? The Gaia hypothesis: biological diversity creates stability in the biosphere: interactions of life with its environments can control the average temperature of the surface, the salinity of the oceans and the carbon dioxide content of the atmosphere and keep them constant via a network of negative feedback cycles. •Example: The daisyworld computer model http://library.thinkquest.org/C003763/flash/gaia1.htm

Why is life so diverse?

The daisyworld computer model of biosphere

•Starting conditions •A cold planet with seeds of black daisies and white daisies •A sun that will continuously warm the planet

•When a minimum temperature is reached, the seeds produce white and black daisy flowers

•But black daisies better absorb light they multiply better

•When the world warms further, daisyworld may overheat

•But white daisies better reflect light multiplication of white daisies stops overheating Temperature on daisyworld is stabilized

T i m

e

•In daisyworld, a continued increase in solar energy is buffered by the changing ratio of black and white daisies.

http://gingerbooth.com/courseware/daisyball.html

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• Biodiversity can be both beautiful and overwhelming.

• Taxonomy is the branch of biology that names and classifies species.

– It formalizes the hierarchical ordering of organisms. (분류를 일정하게 함)

Next time: A brief overview of biodiversity

Summary – The subject of biology • The subject of biology is the study of life, but this subject remains poorly defined.

•A minimalistic and widely accepted definition of life has not yet been formulated. •Life is mainly described by a combination of properties, such as order, conversion of energy and matter, homeostasis, individual and group adaptation, reproduction, and growth and development.

• Because of the many aspects of interest, biology has specialized into many sub-sciences

•For example, by level of organization, category of organism, development, history, physics, chemistry, information, regulation, dysfunction, human species

• The smallest unit of life is the cell, which comes in two structural versions: Prokaryotes

and eukaryotes. It is debatable what the largest unit of life is.

• The main molecules of life (molecules that are normally synthesized by organisms only) include nucleic acids, proteins, sugars, and lipids. These molecules are principally similar in all known forms of life.

• Life is extremely diverse. Diversity is driven by geological evolution and likely helps to maintain planetary homeostasis.

요약 - 생물학의 주제

• 생물학의 주제는 생명에 관한 연구이나, 이들의 주제는 거의 정의되지 않았다.

• 단순하면서 넓게 용인된 생명의 정의는 아직 형식화되지 않았다.

• 생명은 주로, 질서, 에너지와 물질의 변환, 항상성, 개체와 집단 적응, 생식, 생장, 발생과 같은 특징들의 조합으로 설명된다.

• 생물학은 흥미로운 면을 많이 가지고 있기 때문에, 여러 가지 세부 과학으로 특성화되었다.

• 예를 들면, 조직의 단계, 유기체의 범주, 발달, 역사, 물리, 화학, 정보, 조절, 기능장애, 인간 종족 등이 있다.

• 생명의 가장 작은 단위는 세포이며, 구조적으로 두 가지로 분류할 수 있다: 원핵생물과 진핵생물. 생명의 가장 큰 단위가 무엇인지는 논란의 여지가 있다.

• 생명체를 이루는 주된 분자들은 (오직 유기체에 의해서만 일반적으로 합성되는 분자들) 핵산, 단백질, 당, 그리고 지질이다. 이 분자들은 모든 생명체에서 거의 비슷하다.

• 생명체는 매우 다양하다. 다양성은 지질학적 진화에 의해 진행되며, 아마도 행성의 항상성 유지에 도움이 될 것이다.