mrs saba shadab rais paper i, unit i sybsc, semiv …

ORIGIN AND EVOLUTION OF LIFE

SYBSc, SEMIVPaper I, Unit I

MRS SABA SHADAB RAISASST. PROF. Zoology Dept.

RIZVI COLLEGE OF ARTS SCIENCE & COMMERCE

Organic Evolution

MRS SABA SHADAB RAIS2

⚫ The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother.

⚫ Biological evolution, simply put, is descent with modification.

⚫ Small-scale evolution (changes in gene frequency in a population from one generation to the next)

⚫ Basically offspring displays different traits than parents

⚫ Large-scale evolution (the descent of different species from a common ancestor over many generations).

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ORIGIN OF THE UNIVERSE


⚫ big – bang theory⚫ Chemical evolution

A) Miller Urey ExperimentB) Oparin and Haldane theory

1920’s Alexander Oparin and John Haldane: postulated conditions of early earth


Theory of primordial Soup


⚫ Hypothesized the early conditions of earth⚫ Boiling oceans, volcanic eruptions, lightning

storms⚫ Atmospheric gases methane (CH4), ammonia

(NH3), hydrogen (H2), and water (H2O). ⚫ Energy sources electric current through

lightning storms and sun’s UV light⚫ Early earth’s conditions interacted to form

amino acids and small nucleic acids

Miller-Urey Experiment


⚫ First flask partially filled with water and heated to produce water vapor (sea)

⚫ Water vapor was moved to a second flask where methane and ammonia vapor was added (atmosphere)

⚫ Electric sparks (lightening) in second flask was energy source for chemical reactions

⚫ Below second flask, water vapor cooled (rain) and recycled to first flask (sea)

⚫ Result: turned brown with amino acids and other complex organic molecules

Origin of Life


⚫ Stage 1 : Formation of amino acids and large macromolecules thereon

⚫ Stage 2: Formation of coacervates⚫ Stage 3: Formation of functional primitive

cell capable of metabolism⚫ Stage 4: Formation of primitive

autotrophic cell and further different types of organisms

Early Evolution and Rise of O2


⚫ First organisms had simple metabolism⚫ Atmosphere was O2 free, must have been

anaerobic⚫ Probably chemoheterotrophs⚫ Obtained nutrients from organic material⚫ Obtained nutrients from inorganic material⚫ Modern archaea appear to be close to the root of the

tree of life⚫ Obtaining energy from chemical reactions involving

hydrogen, sulfur and iron compounds (all abundant on early Earth)

Early Evolution


⚫ Natural selection probably resulted in rapid diversification

⚫ Modern DNA has enzymes that reduce the rate of mutations

⚫ RNA is not so lucky, more likely to have copying errors

⚫ Higher mutation rate in early evolution than now

Photosynthesis


⚫ Most important new metabolic process evolved gradually

⚫ Organisms that lived close to ocean surface probably developed means of absorbing sunlight (UV in particular)

⚫ Once absorbed, developed method of turning it into energy⚫ Modern organisms of purple sulfur bacteria

and green sulfur bacteria much like early photosynthetic microbes, use H2S instead of H2O for photosynthesis

Photosynthesis


⚫ Using water for photosynthesis developed later, perhaps 3.5 billion years ago

⚫ First appearing in cyanobacteria (blue-green algae)

⚫ By product of O2, released into atmosphere⚫ Changed the world!

Rise of O2


⚫ O2 is highly reactive⚫ All initial O2 would react with rock and minerals

in water⚫ O2 could not accumulate in atmosphere until

surface rock was saturated⚫ Rocks 2-3 bill. Yr old called banded iron

formations, show atmosphere had <1% of current amount of O2

⚫ Rock evidence suggests that O2 amounts in atmosphere began to rise about 2.0 bill. Yr ago

⚫ Clear evidence of O2 near current levels appears only 200 million yr ago ⚫ Find charcoal (fossil fuel)⚫ Indicates enough O2 in atmosphere for fires to burn

Rise of O2


⚫ Rise of O2 would have created a crisis for life

⚫ O2 reacts with bonds of organic materials⚫ Surviving species avoided effects of O2

because they lived or migrated to underground locations⚫ Many anaerobic microbes found in such

locales today

Origin of Eukaryotes


⚫ Fossil evidence dates to 2.1 bill. Yr ago⚫ Dates to when O2 rising in atmosphere⚫ DNA evidence suggests that prokaryotes and

eukaryotes separated from common ancestor much earlier

⚫ O2 played a key role in eukaryote evolution⚫ Cells can produce energy more efficiently using

aerobic metabolism than anaerobic metabolism⚫ Adaptations of aerobic organisms could develop

adaptations that required more energy that would be available for anaerobic organisms

Evidences in Favour of organic evolution


⚫ Geographical distribution⚫ Paleontology⚫ Anatomy

Planetology


⚫ Leonardo da Vinci – Father of Paleontology

Types of Fossils:1. Entire organism2. Petrification3. Cast or Mould4. Compression5. Impression

Entire organism


Fossil lived about 50,000 yrs ago at cold, snowy part

Compression


Plant fossil – outline of thin carbon film of internal structure of plant body reserved in sedimentary rocks

Anatomical Evidences of evolution


1. Homologous Structure2. Analogous structure3. Vestigial organs4. Connecting links


1. Homologous Structures-bodily structures that are similar in structure, but different in function, due to sharing a common ancestor

Homologous Structures


2. Analogous Structures


⚫Analogous structures- bodily structures that are similar in function, but not in structure. NOT EVIDENCE OF COMMON ANCESTRY.⚫Example: wings of a bee

and wings of a bird

3.Vestigial Structures


⚫Structures that serve no function but useful structures in earlier ancestors⚫Examples: Ear muscles⚫Human tailbone ( Coccyx )⚫Appendix


http://en.wikipedia.org/wiki/Image:Stomach_colon_rectum_diagram.gif

Vestigial Organs


4.Connecting link - Archeopteryx


Evidences from Embryology


⚫ Embryo- fertilized egg that will/is in the process of growing into a new individual

⚫ Closely related organisms go through similar developmental stages early in development⚫ All vertebrates have gill pouches sometime

during their early development

MRS SABA SHADAB RAIS

36

http://www.cord.edu/faculty/landa/courses/b315f99/sessions/phylogeny/embryology.jpg

Evidences from Embryology


1. Comparison of early stages of development

2. Comparison of embryo of different animals

38 MRS SABA SHADAB RAIS

Recapitulation Theory


1. Development of frog: frog larva swims like fish it shows that they are evolved from fish

2. Development of Herdmania: tadpole larva of Herdmania shows characters of chordates while adult is urochordate

Development of frog


Development of Herdmania


Evidences from physiology


⚫ Composition of protoplasm of all animal is same therefore similar physiological process

⚫ Similarities in basic process like glycolysis, Krebs cycle , Electron transport Chain etc.

⚫ Fresh water fish and frog tadpole excrete ammonia while adult amphibian and birds embryo excrete urea while adult birds excrete uric acid

⚫ George Nottal precipitin test – human chimpanzee blood similarity

Evidences from genetics


o DNA used to translate nucleotide sequences into amino acid is essentially the same in all organisms

o Proteins in all organisms are composed of the same set of 20 amino acids

o Powerful argument in favor of the common descent of the most diverse organisms.

http://www.neanderthal-modern.com/images/dna.gif

Theories of organic evolution


Jean-Baptiste de Lamarck (1744 - 1829)was also a student of Buffon. Like Buffon, Lamarck sought a naturalistic explanation for the diversity of modern organisms and the animals seen in the fossil record.Lamarck used the theory of Inheritance of Acquired Characteristics, a widely-held belief at the time, to explain change in organisms. Blacksmiths, for example, were thought to pass their well-developed right arms on to their sons.


Lamarck’s Organic Theory of Development

Organisms are shaped by their environment.

Change is goal-directed -- organisms have an internal drive to become more and more complex.Use and disuse of parts causes change that is passed on from generation to generation.


Charles Darwin (1809 - 1882)and Alfred Russell Wallace (1823 - 1913)

Darwin and Wallace, working separately, devised a model for organic change that was based on their observations of living and fossil organisms over many years. Natural Selection was the first evidence-based mechanism for evolution that was proposed.


Darwin and Wallace observed that change did not happen equally to all members of a population, as Buffon and Lamarck thought.


Instead, Darwin and Wallace proposed that selection happens each generation. Some individuals have traits that help them survive and reproduce, while others have traits that put them at a disadvantage.

Over generations, the number of individuals with favorable traits increases while those with unfavorable traits decrease.


Darwin’s observations


⚫ Specifically he paid close attention to the finch birds on each island

⚫ He looked at their beaks⚫ He determined that each finch had a

different beak shaped specifically for the food which was available to them

⚫ He also noticed that finches on the Galapagos resembled finches in similar environments in other parts of the world

Darwin’s observations


⚫ Overproduction⚫ Competition⚫ Variation⚫ Survival of the fittest

Overproduction


⚫ Species produce many more offspring than environment can support

⚫ Population size is limited by: space, food supply, disease, predators,

etc.

Variation


⚫ In any sexual reproducing species, there are differences within individuals

Competition


⚫ Not only do individuals within a population compete but different species with similar needs compete

⚫ Intraspecies competition: within one's own species

⚫ Interspecies competition: between two different species

Struggle for Existence


⚫ Overproduction of offspring creates competition for survival between the members of the species

Survival of the fittest


⚫ Fitness: refers to physical or behavioral characteristic that helps survival

⚫ The most fit individuals are those capable of getting the food, shelter, females etc.


⚫ Overproduction causes competition⚫ There are too many individuals⚫ The environment cannot maintain

⚫ Individual variation causes different methods of survival⚫ The variation with the greatest chance of

survival is said to be the fittest⚫ These individuals survive and reproduce

passing the fit trait to their offspring⚫ Over a period of time this shifts the

observed phenotype in the population (evolution)

⚫ NATURE CHOOSES FITNESS

Neo-Darwinism


⚫ Modified form of Darwin theory⚫ 1880 doubts started creeping about its

validity and application⚫ Modern theory of Origin of species is

known as Modern Synthetic theory of Evolution or Neo Darwinism

⚫ 20th century new ideas on evolution followed by rediscovery of Mendle’s law of Heredity by Hugo de Vries and others

Neo-Darwinism


⚫ Hugo de Vries theory of Mutation stated that new species arise due to sudden mutation rather than gradual process

⚫ Wagner suggested that role of geographic or spatial isolation in formation of species, race or tribe of animals or plants

⚫ Moreover in certain population there is struggle for space, food and water and has definite stability

⚫ Evolution in organism occurs over the long period of time for many generations

⚫ Thus unit of evolution is recognized by not the individual but population

Mutation theory


Hugo de Vries proposed that species arise due to sudden mutation rather than gradual process

1. In a naturally breeding population or species mutation occur from time to time amongst the individuals. The individuals with mutation are known as mutants, which are distinct from their parents.

2. Mutation are heritable and create new species or races. They do not disappear by crossing.

3. Mutations are all a sudden and not a gradual process.

Mutation theory


4. Mutation occur possibly in all do not involve same character,

5. By natural selection the unsuitable mutants are destroyed,

Weismann’s Germplasm theory


Modern synthetic theory




⚫ It states that genes are units of heredity which transmit characteristics from one generation to another and they are capable of mutation as well as recombination

⚫ Mutations can be harmful or useful, harmful eliminated by natural selection. However favorable mutations help the organism to adapt to their surrounding thus making them fit for survival.

⚫ Modern synthetic theory has basis of mutation – adaptation – selection phenomenon.



⚫ Eg. Camel and llama two closely related species

⚫ Camel desert species while llama high altitude species

⚫ Hb found in this two species have different affinity for oxygen

⚫ Changes in organism enabled them to acquire specialization to adapt to their surrounding get selected by nature

Neutral theory of molecular evolution


⚫ Motoo Kimura 1968⚫ The neutral theory of molecular

evolution holds that most evolutionary changes at the molecular level, and most of the variation within and between species are due to random genetic drift of mutant alleles that are selectively neutral.

mrs saba shadab rais paper i, unit i sybsc, semiv …

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