EVOLUTION THROUGH TIME GENERAL BIOLOGYIO.pptx

This includes some information about evolution of organisms in general.

1. EVOLUTION Dr. Michelle A. Ventura Medical Biology Department SAS

2. EVOLUTION is the process of gradual developmental modification so as to establish diversity and complexity in the living world; the present day complex plants and animals have evolved from earlier simpler forms of life by gradual changes  https:// www.geeksforgeeks.org /human-evolution-stages/    

3. SEQUENTIAL EVOLUTION Reflecting the conservative nature of biological inheritance, the evolution of modified gene pools from pre-existing ones is called sequential evolution by paleontologists, working with short-time series, geneticists studying laboratory populations and field biologists investigating isolated natural populations are all examples of sequential evolution. DIVERGENT EVOLUTION When individuals in one species, or closely related species acquire enough variations in their traits that lead to two new distinct species. In divergent evolution, two or more distinct species share a common ancestor from which they diverged. A common example is  a modern elephant and woolly mammoth . They share a common ancestor and yet evolved into two different species. Another example is the dog, the wolf, and the fox. https://www.biologyonline.com/dictionary/divergent-evolution

4. MICROEVOLUTION-the evolution of subspecies or geographic races MACROEVOLUTION-the evolution of species and genera of higher categories MEGA EVOLUTION- is for large-scale evolution, operating at the level of families, orders, classes, and phyla

6. THEORIES OF EVOLUTION LAMARCKISM OR Theory of Inheritance of Acquired Characters DARWINISM OR Theory of Natural Selection MUTATION THEORY OF DE VRIES NEO-DARWINISM OR MODERN CONCEPT OF SYNTHETIC THEORY OF EVOLUTION

7. POSTULATES OF LAMARCKISM New needs Use and disuse of organs Inheritance of acquired characters Speciation

8. SUMMARY OF POSTULATES OF LAMARCKISM: Living organisms or their parts tend to increase in size. Production of new organs results from a new need. Continued use of an organ makes it more developed, while disuse of an organ results in degeneration Acquired characters (or modifications) developed by individuals during their lifetime are inheritable and accumulate over a period resulting in new species

9. EVIDENCE IN FAVOR OF LAMARCKISM   PHYLOGENETIC STUDIES of horses, elephants, and other animals show that all these increase in their evolution from simple to complex forms.

10. https://atlasofscience.org/evolution-of-aquatic-mammals-and-birds-the-present-predicts-the-past/

11. These changes were induced due to a food deficiency on land and severe competition. It is an example of both extra use (skin between the toes) and disuse (wings) of organs. https://en.wikipedia.org/wiki/Evolution_of_birds

12. CRITICISM OF LAMARCKISM August Weismann proposed the “Theory of Continuity of Germplasm” in 1892 A.D. This theory states that environmental factors affect only somatic cells and not the germ cells He suggested that germplasm is with special particles called “IDs” which control the development of parental characters in offspring. Weismann mutilated the tails of mice for about 22 generations and allowed them to breed but tailless mice were never born.

13. NEO-LAMARCKISM Long-forgotten Lamarckism has been revived as NEO-LAMARCKISM in the light of recent findings in the field of genetics which confirm that environment does affect the form, structure, color, size, etc. and these characteristics are inheritable.

14. NEO-LAMARCKISM states Germ cells may be formed from the somatic cells indicating a similar nature of chromosomes and gene make-up in two cell lines e. g. Regeneration in earthworms Vegetative propagation in plants like Bryophyllum (with foliar buds) A part of the zygote (equipotential (egg) of a human female can develop into a complete baby (Driesch). 2. The effect of the environment on germ cells through the somatic cells 3. The effect of environment directly on germ cells. Tower exposed the young ones of some potato beetles to temperature fluctuation and found that though beetles remained unaffected with no somatic change the next generation had marked changes in body coloration.

15. NEO-LAMARCKISM proved: Germ cells are not immune from the effects of the environment. Germ cells can carry somatic changes to the next progeny (Harrison’s experiment) Germ cells may be directly affected by environmental factors (Tower’s experiment).

16. DARWINISM ( THEORY OF NATURAL SELECTION) CHARLES DARWIN (1809-1882 A.D.), an English naturalist The main postulates of Darwinism are: Geometric increase Limited food and space Struggle for existence Variations Natural selection of Survival of the fittest Inheritance of Useful variations Speciation

17.   Overproduction All species have a tendency and the potential to increase at a geometric rate. All organisms produce more organisms but only a few survive.   2. Competition Due to environmental pressures, the organisms within a population must compete with each other to survive. 3. Variation Individuals in a population vary greatly in their characteristics 4. Adaptation Individuals who best adapt to the environment are the ones who will most likely survive 5. Natural selection Individuals having favorable traits will produce more offspring, and those with unfavorable traits will produce fewer offspring 6. Speciation The process in which new genetically distinct species evolve usually as a result of genetic isolation from the main population.

18. EVIDENCES IN FAVOR OF DARWINISM There is a close parallelism between natural selection and artificial selection Correlation between position of nectaries in the flowers and length of the proboscis of the pollinating insect. The main difference between the two theories is the manner by which change occurs. While Darwin believed that changes occur by chance at birth when the organisms were born, Lamarck believed that change occurs throughout the organism's lifestyle as they adjust to the numerous changes in their environment.

20. III. MUTATION THEORY OF EVOLUTION The mutation theory of evolution was proposed by a Dutch botanist, Hugo de Vries (1848-1935 A.D.) (in 1901 A.D. in his book entitled, “ Species and Varieties, Their Origin by Mutation.” Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while apparently unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution.  Wikipedia Born:  February 16, 1848,  Haarlem, Netherlands Died:  May 21, 1935 (age 87 years),  Lunteren, Netherlands https://www.dnaftb.org/6/bio.html

21. He worked on evening primrose

22.   Evolution is a discontinuous process and occurs by mutations individuals with mutations are called mutants. Elementary species are produced in large numbers to increase the chances of selection by nature. Mutations are recurring so that the same mutants appear again and again. This increases the chances of their selection by nature. Mutations occur in all directions so may cause gain or loss of any character.

23. EVIDENCES OF MUTATION THEORY

24. IV. NEO-DARWINISM OR MODERN CONCEPT OR SYNTHETIC THEORY OF EVOLUTION POSTULATES OF NEO-DARWINISM THEORY Genetic variability: Various sources of genetic variability in a gene pool are: Mutations Recombination of genes: Thousands of new combinations of genes are produced due to crossing over, chance arrangement of bivalents at the equator during metaphase, and chance fusion of gametes during fertilization Hybridization: It involves the interbreeding of two genetically different individuals to produce “hybrids” Physical mutagens (e.g. radiations, temperature, etc.) and chemical mutagens (e.g. nitrous acid, colchicine, nitrogen mustard, etc ). Genetic drift: It is the elimination of the genes of some original characteristics of a species by an extreme reduction in a population due to epidemics or migration or Sewell Wright effect. The chances of variations are also increased by non-random mating.

25. https://www.canr.msu.edu/news/is-it-natural-genetic-variation-or-genetic-modification

26. 2. Natural Selection: Natural selection of Neo-Darwinism differs from that of Darwinism in that it does not operate through “survival of the fittest” but operates through differential reproduction and comparative reproductive success.

27. Reproductive Isolation: Any factor which reduces the chances of interbreeding between the related groups of living organisms is called an isolating mechanism

28. MECHANISMS OF EVOLUTION Mechanisms of Evolutionary Change: 1. Natural Selection 2. Genetic Drift 3. Mutation 4. Gene Flow

29. Natural Selection This leads to an evolutionary change when some individuals with certain traits in a population have a higher survival and reproductive rate than others and pass on these inheritable genetic features to their offspring. Evolution acts through natural selection whereby reproductive and genetic qualities that prove advantageous to survival prevail into future generations. The cumulative effects of the natural selection process have given rise to populations that have evolved to succeed in specific environments. Natural selection operates by differential reproductive success (fitness) of individuals.

30. GENETIC DRIFT -i s a random event that happens by chance in nature that influences or changes allele frequency within a population as a result of sampling error from generation to generation. It may happen that some alleles are completely lost within a generation due to genetic drift, even if they are beneficial traits that conduct to evolutionary and reproductive success. Allele is defined as any one or two or more genes that may occur alternatively at a given site (locus) on a chromosome. Alleles are responsible for variations in a trait.

31. MUTATION can be defined as a change in the DNA sequence within a gene or chromosome of a living organism. Many mutations are neutral, i.e. they can neither harm nor benefit, but can also be deleterious or beneficial.

32.     According to their magnitude, mutations can occur at different levels: Gene mutations-any change in the sequence of nucleotides of the genetic material of an organism Chromosome mutations- a change in the structure or arrangement of the chromosomes These mutations can involve duplications or deletions of chromosome segments, inversions of sections of DNA (reverse positions) and translocation. Genome mutations-are alterations in the number of chromosomes in the genome. They can be classified into 2 groups: Aneuploidy-the losses and/or gains of individual chromosomes from the normal chromosome set arising from errors in chromosome segregation Euploidy-variations in complete sets of chromosomes

33. GENE FLOW - also known as gene migration in population genetics, refers to the transfer of genes from the gene pool of one population to another. Gene flow may change the frequency and/or the range of alleles in the populations due to the migration of individuals or gametes that can reproduce in a different population.

34. ISOLATION TEMPORAL ISOLATION-a type of isolation that occurs when populations do not interbreed with each other because they reproduce at different times MECHANICAL ISOLATION- a type of isolation that occurs when different species are isolated by their mechanics BEHAVIORAL ISOLATION-a type of isolation in which 2 allopatric species do not mate because of different courtship behavior REPRODUCTIVE ISOLATION- a type of isolation that occurs when 2 groups of animals live close enough to one another to interact but are unable to interbreed with one another ECOLOGICAL ISOLATION- a type of isolation when organisms have the same range but do not come across one another because they are eating different food, living in different habitats, or are mating in different areas. GEOGRAPHIC ISOLATION- a type of isolation when a population split apart by a physical barrier such as a river, ocean, mountain range,etc .

35. EVIDENCES OF EVOLUTION Direct evidences Paleontological evidences Indirect evidences Comparative anatomical evidences Taxonomical evidences Comparative embryological evidences Comparative physiological evidences Genetic evidences Biogeographical distribution evidences

36. EVIDENCES FROM COMPARATIVE ANATOMY Analogy and homology Analogy-similarity of function and superficial resemblance of structures that have different origins Homology- are those which have a common origin that is modified as per different functions

37. CONNECTING LINKS VIRUSES ( LIVING AND NON-LIVING) EUGLENA (plants and animals) Proterospongia (Protozoans and Porifera) Neoplina (Annelida and Mollusca) Peripatus (Annelida and Arthropoda) Balanoglossus (Non-chordates and Chordates) Lung Fish (Fishes and Amphibians) Archaeopteryx (Birds and Reptiles) Egg-laying mammals (Reptiles and Mammals)

38. EVOLUTION EVIDENCE: COMPARATIVE EMBRYOLOGY

39. COMPARING DNA DNA sequences are the strongest evidence for evolution from a common ancestor. The diagram is a cladogram, a branching diagram showing related organisms. Each branch represents the emergence of new traits that separate one group of organisms from the rest and shows how humans and apes are related based on their DNA sequences.

40. CLADOGRAM

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