Download General_Biology_lecture_3-_Spring_2014

Last time:
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The subject of biology
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Definition of life
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Fields of life sciences
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The units, molecules, and diversity of life
Today:
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Overview of life forms
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The unity in the diversity of life
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The theory of evolution explains and connects unity and diversity
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Evolution and engineering: Life versus machines
A brief overview of biodiversity
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Taxonomy is the branch of
biology that names and
classifies species.
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It formalizes the
hierarchical ordering
of organisms.
(분류를 일정하게 함)
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Three Domains of Life
• The three domains (영역) of life are:
(=“Archaebacteria”)
An extraterrestrial look at life on Earth
• The lengths of the lines are mathematical estimates
of the evolutionary distance
• There is not much difference between a human and
a yeast!
Most organisms are microbes = microscopically small
Some organisms are multicellular
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Microbes make up about ½ of the earth’s biomass (6x1030 microbes on earth)
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Animals make up 1/1000th of the earth’s biomass
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Each ml of seawater contains 1 million bacteria and 10 million viruses
This slide is important
– please know it well
Prokaryotes
Eukaryotes
The domain Eucarya (= eukaryotes) includes at least four kingdoms
Kingdoms:
– Animalia
– Fungi
– Plantae
– ….
– ….
– ….
– ….
– ….
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Protists
(multiple kingdoms)
Main features of the eukaryotic kingdoms
- Protists
Single-celled eukaryotes
• Protists are very diverse
- Plantae:
produce sugars by photosynthesis
• Protists are not fundamentally
different from plants, animals, fungi
-Fungi:
mostly decomposers
• Plants, fungi, and animals may be
seen as colonial (multicellular)
forms of some of the protists
-Animalia:
gain food by ingestion
• Origin of plants = immobile colonies of photosynthetic
protists
• Origin of fungi = immobile colonies of consumer
(decomposing) protists (usually parasitic)
• Origin of animals = mobile colonies of consumer-type
protists
http://cnx.org/content/m44658/latest/#fig-ch27_03_01
The simplest known animals are the sponges. Sponges likely are a colonial version of a type
of protists called choanoflagellates.
Unity in the Diversity of Life
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Underlying the diversity of life is a striking unity, especially at the lower levels of
structure.
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Universal genetic language of DNA (was mentioned last time)
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Similarities in chemical compositions (will be discussed soon)
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Similarities of key metabolic pathways (will be discussed in a few weeks)
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Similarities of ultrastructure
Example of similar ultrastructure: The universal architecture of eukaryotic cilia
(a)
Paramecium
(A protist)
(b) Cells from
Cilia on cells of
fallopian
the lung
tube
(Animal cell types)
(c) Cross section of cilium
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Evolution: Biology’s Unifying Theme
What can account for this combination of unity and diversity in life ?
⇒ evolution
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Fossils document that life has changed
dramatically over Earth’s history
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
•Fossils also show that different species have common ancestors ( “tree of life”)
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Darwinian View of Life
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The modern view on evolution:
Charles Darwin’s book The
Origin of Species (1859).
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
•
Darwin was struck by the diversity of
animals on the Galápagos Islands.
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Different islands have 14 different species
of Galápagos finches with beak shapes
adapted to suit their different environments.
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Darwin already knew concepts of geology
and understood that the Galapagos islands
are “young”
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He realized that adaptation to the
environment and the origin of new species
are related processes.
•
(Today the molecular basis of the different
beak shapes is known)
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Darwin synthesized his theory of evolution from
two facts that everybody knew and knows.
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Fact 1: Overproduction and competition
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Fact 2: Individual variation (“Descent with
modification”)
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The inescapable conclusion: Unequal
reproductive success
•
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Darwin called this unequal
reproductive success natural
selection.
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The product of natural selection is
adaptation.
Natural selection is a key mechanism of
evolution (additional mechanisms were
discovered after Darwin).
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Darwin also understood artificial selection; this knowledge contributed to his theory
Wild mustard
Kale
Cauliflower
Red
cabbage
Broccoli
Brussel’s sprout
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Wolves
Natural selection is still going on
Example: The development of antibioticresistant bacteria
Tuberculosiscausing bacteria
• Emergence of antibiotic-resistant bacteria does not mean that the drugs created the
favorable characteristics.
• Rather, the environment screened the heritable variations that existed among individuals
of a population and favored the ones best suited to present conditions.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Alternative explanations for the origin and diversity of species
• Inheritance of acquired adaptation “(Lamarckism”)
• Example: A father who exercises his muscles produces
children with stronger muscles
requires a mechanism by which muscle cells
instruct sperm cells or eggs
 No such mechanism has been found
J. Lamarck (1744-1829)
• Other approaches: Full or partial negation of evolution
Creationism (newest variant: “Intelligent design”)
How evolution is studied
•Evolution not recognized
•Anatomy, embryology
Medieval times
1859 Charles Darwin
Origin of Species
1894 Ernst Haeckel
Recapitulation hypothesis
•Ultrastructure
•Sequencing
1966 Lynn Margulis
Endosymbiont hypothesis
After 1960 –many scientists
Note: These are the same methods that describe the diversity of life
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Darwin’s publication of The Origin of Species fueled an explosion in
biological research.
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Evolution is one of biology’s best demonstrated, most comprehensive, and
longest lasting theories.
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Evolution is the unifying theme of biology.
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The catholic church also accepts evolution.
“Nothing in biology makes sense except in the light of evolution. ”
Theodosius Dobzhansky, 1973
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Note parallel with human history:
Human society cannot be understood without knowing history.
Examples illustrating the thesis of Dobzhansky
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Overproduction of sperm.
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Each human produces typically less than 10 children.
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Every man produces billions of sperm cells – a huge waste.
– WHY?
– The sperm cells are not identical ! (“descent with modification”)
– Production of billions of different sperm cells maintains the ability of the
species Homo sapiens to adapt (details in the second half of the semester)
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Junk DNA.
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Less than 5% of our DNA contains useful genetic information.
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WHY?
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The “junk” DNA is a “playground” for evolution = provides flexibility for
genetic change
After Darwin
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Progress within Darwin’s concept
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New concepts
Progress within the Darwinian concept
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A more detailed picture about
– Diversity of life
– Stages of evolution: The “key inventions” leading to modern life are
largely known (steps of chemical evolution, cellular evolution,
multicellularity)
– Timing of evolution
– Forces driving evolution
The time scale of macroevolution as currently known
http://en.wikipedia.org/wiki/File:Geologic_Clock_with_events_and_periods.svg
The principal driving force of evolution
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The ultimate driving force of biological evolution is geological evolution (plate
tectonics)
http://en.wikipedia.org/wiki/File:TectonicReconstructionGlobal2.gif
• However, biological evolution acts back on lithosphere and atmosphere and so
influences its own further evolution
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Example: Oxygen in the atmosphere (20%) results from life processes
Conceptual advances made after Darwin
• Genetic information comes in discrete units (genes) that are packaged in clusters
(chromosomes) that can be recombined
• Cellular and molecular nature of “modification”:
– Nature of sex (recombination of chromosomes)
– Mutations (heritable changes of the genes = changes in the text; example:
AGCCTAAC  AGGCTAAC)
• Additional mechanisms of evolution:
– Cooperation (game theory predicts that cooperation may give an advantage over
simple competition)
– Lateral gene transfer (= the movement of genetic information from one species to
another species)  refinement of the concept of the Tree of Life
• The fundamental mechanisms of evolution currently known:
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–
–
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Descent with modification (based on genes, chromosomes, and mutations)
Selection (based on overproduction and competition)
Cooperation (based on game theory)
Lateral gene transfer (based on the discovery of mobile genetic elements)
Evolution and engineering: Life versus machines
Evolution as an engineer: Example - The stepwise “invention” of mammals
T I M E
Organisms live in order to live
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But evolution is stupid and blind: It doesn’t have a purpose or goal  Organisms
don’t have a “purpose” or “goal” in life except of reproduction (otherwise life would
disappear)
• A machine is a tool that consists of one or more parts, and uses
energy to meet a particular goal. (Wikipedia)
 machines are optimized for a specific, narrow goal, don’t have “unnecessary” parts
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Therefore, organisms are not just machines. The only “goal” or “purpose” of their
existence is their existence!
Summary – The diversity, unity, and evolution of life
•Life is organized into three domains: bacteria, archaea, and eukarya
•Millions of species are known to exist.
•Most life forms are microbial.
•Multicellular life forms (animals, fungi, plants) are closely positioned on the tree of life.
•Multicellular life forms are colonial versions of eukaryotic cells that also exist as single cells (protists).
•Unity: All life forms share the DNA language, principal chemical compositions, metabolic
pathways, and some ultrastructural designs.
•Evolution from a common origin explains both unity and diversity of all known life forms
•Charles Darwin is credited for developing the successful scientific concept of evolution.
•According to Darwin, the mechanism of evolution includes overproduction and individual variation,
leading to natural selection and adaptation.
• The main driving force of evolution is a changing environment. Evolution does not stop.
•Recent conceptual advances in understanding evolution
•Genetic information comes in discrete units (genes and chromosomes).
•Individual variation is caused by mutations and by sex (genetic recombination).
•Newly recognized mechanisms of evolution include cooperation and lateral gene transfer.
•Evolution versus engineering
•Evolution may (but does not have to!) lead to remarkable designs that often inspire engineers (bionics).
•However, evolution is blind and has no purpose (the only “purpose” of life is to maintain its existence).
•By contrast, human engineering has a narrow purpose. Therefore it is often possible to make machines
that are better than life for a narrow purpose.
요약- 생명의 다양성과 통일성, 그리고 진화
• 생명체는 세 개의 영역으로 조직된다: 세균, 고세균, 진핵생물.
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•
•
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수백만 종들이 존재하는 것으로 알려져 있다.
대부분의 생명체는 미생물이다.
다세포 생명체는 (동물, 균류, 식물) 생물의 계통수에서 가깝게 위치하고 있다.
다세포 생명체는 진핵세포의 군체들이며, 진핵세포는 또한 단세포로서도 존재한다 (원생생물).
• 통일성: 모든 생명체는 DNA 언어, 기본 화학 구성성분, 대사경로, 그리고 일부 초미세구조적 설계
가 공통적이다.
• 공통 기원으로부터 진화는 알려진 모든 생명체의 통일성과 다양성을 설명한다.
• 찰스 다윈은 진화를 성공적인 과학적 이론으로 개발한 공로를 인정받았다.
• 다윈에 따르면, 진화의 기작은 과잉생산과 자연 선택, 적응에 따른 개체 변이를 포함한다.
• 진화를 유발하는 주된 힘은 환경의 변화이다. 진화는 지금도 끊임없이 계속된다.
• 진화 이해에 대한 최근 개념적 진보
• 유전적 정보는 별개의 단위에 저장된다 (유전자와 염색체).
• 개체간 변이는 돌연변이와 성(유전적 재조합)에 의해 유발된다.
• 최근에 인식된 진화의 기작은 협력과 측면 유전자 전이를 포함한다.
• 진화 Vs 공학
• 진화는 종종 공학자에게 감명을 줄 수 있는 놀라운 설계로 이끌 수도 있다 (생체공학).
• 그러나, 진화는 장님이며, 목적이 없다 (생명의 유일한 “목적” 은 그것의 존재를 유지하는 것이다).
• 대조적으로, 공학자는 좁은 목적을 가지고 있다. 결과적으로 그것은 좁은 목적에 대해서 종종 생명보다 나
은 기계를 만들 수도 있다.