Microsoft PowerPoint - Week09-1-Species Concept and ETC

종의개념 Species Concept

대체 Species: (1) 자연철학적인종의인식 Plato (BC 428/427 348/347) - idea론 : 형이상학이론. 이데아는현상세계밖의세상이며이데아는모든사물의원인이자본질이다. 예를들면인간의이데아는현실세계의인간에대한원인으로, 인간의이데아가있기때문에현상세계에인간이실재하는것을들수있다. - 현상세계에서모든것들은낡고사라지는것에반해, 이데아는시간에도그모습을변치않으며현상세계의사물들이궁극적으로되고자하는것. Aristotele (BC 384-322) - 종이란생물을이루는 idea를뜻하며, 개체는이러한 idea가물질을바탕으로하여구체적인실체가된것이라표현함.

Species: (2) 유형학적종의개념 (Typological species concept) = 분류학적종의개념, 형태학적종의개념, 원형적종의개념 Ray 로부터 Linne 까지 - Ray: 종의본질을과학적연구의대상으로써최초로인식 종이란생물의총화로서실제는형태적으로동일하고, 번식으로자손을퍼뜨리며상 호유사성을가진단위 - Linne: 체계적인명명법에의해자연계에존재하는모든생물이 종 이라는기본단위 로구별가능하게됨. 종은자연계에보편적으로존재하며, 지역적으로넓게분포하고있고, 분류의기본단 위가되며, 결코인위적으로창조된의식활동의산물이아니다 이후동종을대표할수있는하나의개체를형상 (eidos) 의원형 (archetype) 으로하여 기준으로삼는 Typological Species Concept ( 유형학적종의개념 ) 의출연. = Morphological Species Concept ( 형태적종의개념 )

Species: (2) 유형학적종의개념 (Typological species concept) Linne에서 Darwin 까지 -Cuvier 만약종이변하는것이라면현재형태의독립성에의해규정되고있는종의독립성은없어질것이고, 종간의경계가모호해지거나소실되고말것임 - 종의존재에대한부정으로발전 무명론적종 (Nominalistic Species) : 존재하는것은개체뿐이다

진화론의대두 Species: (2) 유형학적종의개념 (typological species concept) - Lamark : 종의가변성을구체적으로인식 종이란조금씩단계적으로형성되어나아가며, 변종은시간이지남에따라새로운종 으로발전한다 따라서생물의각분류계급은진화를통해형성되었고, 계통발생적인연속체 (continuum) 을이룬다. 종의실체를파악하여이론화시키지못함 - Darwin 진화론 : 진화는종의변이성과자연선택에의해일어난다. 자연선택 (natural selection) 이란종의형성이외부환경조건에적응하기위하여전생 물이변해가는과정을설명하며, 여기에수반되는새로운종들사이의절연성 (hiatus) 의증대원인을규명하는것이다. 종자체에대한정의는명확하지않음.

Species: (3) 생물학적종의개념 (Biological Species Concept) 종은유전적집단으로구성되어있으며, 그집단을구성하는개체들은하나의생식적공동체 (reproductive community) 를이루고, 따라서그들은고유한생태적지위 (ecological niche) 를지님과동시에, 유전자 pool을공유하는유전적단위 (genetic unit) 가된다는기본적인인식을바탕으로함. Ernst Mayer (July 5, 1904 February 3, 2005) 에의한정의 상호생식적으로격리되며, 현실적또는기능적교배가가능한생물의자연집단군 A species is a group of interbreeding natural populations that is reproductively isolated from other such group.

Ernst W. Mayer Ernst Walter Mayr (July 5, 1904, Kempten, Germany February 3, 2005, Bedford, Massachusetts U.S.), was one of the 20th century's leading evolutionary b iologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist. His work contributed to the conceptual revol ution that led to the modern evolutionary synthesis of Mendelian genetics, systematics, and Darwinian evolution, and to the development of the biological spe cies concept. Neither Darwin nor anyone else in his time knew the answer to the species problem: how multiple species could evolve from a single common ancestor. Ernst Mayr approached the problem with a new definition for the concept species. In his book Systematics and the Origin of Species (1942) he wrote that a species is not just a group of morphologically similar individuals, but a group that can breed only among themselves, excluding all others. When populations of organis ms get isolated, the sub-populations will start to differ by genetic drift and natural selection over a period of time, and thereby evolve into new species. The mo st significant and rapid genetic reorganization occurs in extremely small populations that have been isolated (as on islands). His theory of peripatric speciation (a more precise form of allopatric speciation which he advanced) based on his work on birds, is still considered a leading m ode of speciation, and was the theoretical underpinning for the theory of punctuated equilibrium. Mayr is generally credited with inventing the modern philosop hy of biology, particularly of evolutionary biology, which he distinguished from physics, for its introduction of (natural) history into science.

생물학적종의개념의문제점 Species: (3) 생물학적종의개념 (Biological Species Concept) 1) 적용의한계성 : 식물들은많은경우생식의개념없이개체증식영양번식 (vegetative propagation) - 대부분의다년생피자식물에서일어남 Ex) Scandinvian flora 피자식물중 80% 이상이 vegetative propagation을함 (Gustaffson, 1964). Ex) Redwood tree (Sequoia sempervirens) 80% 이상이 crown sprout로기원. 20% 만이 seedling에의함. Ex) Populus tremuloides : 25 acer에 15,000개체를갖는 clone 형성 - 무수정결실 (agamospermy) : 배우체를만들지않고수정없이 embryo를만들어내는것. ex) 민들레속 (Traxacum) 식물 i) pathenogenesis ( 처녀생식 ): 수정없이 egg ( 알세포 ) 가embryo 로발달 ii) adventitious embryony ( 부정배현상 ): ovule ( 자방, 씨방 ) 내의체세포가 embryo로발달 2) True breeding의문제점 - AX B 5% but B X A 98% - A X B, B X C, C X D, D X E 교배가능그러나 A X E는교배불가능

Populus tremuloides

Species: (4) 진화적종의개념 Evolutionary species concept Simpson (1961) 1) It is a lineage, an ancestral-decendant sequence of populations existing in space and time. 시공에존재하는일련의조상-후손집단들의연속으로서의계보. 2) The lineage evolves separately from other such lineages, that is, from other species. 다른종과같은다른계보로부터분리되어진화한계보. 3) It has its own unitary evolutionary role which is to say that it fits into its own particular ecological niche in a biotic community. 자신의독자적진화적역학 (evolutionary role) 을하는것, 즉생태계에서자신의특수한생태적지위로적응한집단. 4) It has its evolutionary tendencies, being susceptible to change in evolutionary role during the course of its history. 자신만의진화경향성을가져자신의역사경로동안진화적역할을변화시킬수있다. Wiley (1978) Common evolutionary fate through h time ( 교과서의설명 )

Species: (4) the others Recognition Species Concept ( 인식 ) Phenetic Species Concept ( 표현적 ) Apomorphy Species Concept ( 파생형질 ) Diagnostability Species Concept ( 진단적 ) Genealogical Species Concept ( 혈통적 )

- Archaeanthus : 목련의직접조상이라고생각되는약 1 억년전발견된화석 - Ecotype ( 생태형 ): 특수한생태적환경에의해분화된집단 - Vicariance distribution ( 분단분포 ) - Mutation / recombination - Genetic drift ( 유전적부동 ): mutation, hybridization ( 교잡 ), introgression ( 유전자이입 ) 등에의해일어남 - Allopatric specieation ( 이소적종분화 ) / sympatric specieation ( 동소적종분화 ) - Temporal isolation / habitat isolation / floral isolation - Principle Component Analysis (PCA; 주성분분석 ): 형태적형질들을종합적으로분석할때형질 ( 성분 ) 들간의상관관계를형질들의차원축소 를통하여파악하는통계적인기법. - Polyploidy ( 다배체현상 )