EVIDENCES FOR EVOLUTION...............pptx

Evidences for evolution

1. EVIDENCES FOR EVOLUTION Submitted to Submitted by Dr. Chandini V K Cathy Surya Department of Botany 1 st Msc Botany St. Teresas College, Ernakulam 1

2. EVIDENCES FOR EVOLUTION 2

3. EVIDENCES FOR EVOLUTION Evolution is a process of gradual change that takes place over many generations, during which species of animals, plants, or insects slowly change some of their characteristics. Evidences that scientists have gathered in support of evolution [ Topics discussed in this PowerPoint ] Morphology Comparitive anatomy Embrology Physiology 3

4. The traces of patterned cellular structure in rocks (and chemical processes in sediments and atmosphere) that provide the first hard evidence for the presence of life. The alternating light and dark bands of fossil stromatolites (‘living’ rocks found in shallow water that grow in layers consist of photosynthetic microbes, cyanobacteria, and precipitated calcium carbonate) are the earliest evidence of a living process. The earliest plant to show several adaptations for life on land, is Cooksonia 4 Evidences for Evolution

5. MORPHOLOGY AND COMPARITIVE ANATOMY 5

6. EVIDENCES FOR EVOLUTION Darwin thought of evolution as " descent with modification ," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor. In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor . 6

7. Homologous Features Analogous Features Similar Anatomy Dissimilar Anatomy Inherited from a common ancestor Not inherited from ancestors Develops in related species Develops in unrelated species A result of divergent evolution A result of convergent evolution Developed as a result of the adaptation to a different environment Developed as a result of the adaptation to a similar environment 7

8. HOMOLOGOUS FEATURES Homology in animals - Organs such as bat's wing, wings of birds, seal’s flipper, forelimb of a horse, and human arm have a common underlying anatomy that was present in their last common ancestors. Man uses his hands to grasp and perform tasks , whales use their flippers for swimming , bats and birds use their wings for flight and horses use their forelimbs for running . 8

9. HOMOLOGOUS FEATURES Homology in Plants – In some plants like the pitcher, Venus fly trap, poinsettia and cactus, the leaves show different functions and shapes from the ‘normal’. Each of these leaves is a homologous structure, derived from a common ancestral form. The pitcher plant and the Venus fly trap uses leaves to trap and digest insects. The bright red leaves of the poinsettia though leaves, look like flower petals. The cactus leaves are modified into small spines that help reduce water loss and protect the cactus from plant-eaters. 9

10. ANALOGOUS FEATURES Analogy in Animals- The wings of insects, bats and birds are evolved independently in each lineage separately after diverging from an ancestor without wings. The wings of insects originate from the inner or outer surface of the insect’s body. Feathers of birds originate from their forelimbs, and the wings of bats originate from both the fore limb and the membranous skin of the abdomen. 10

11. ANALOGOUS FEATURES Analogy in plants - The leaves of opuntia and Peepal . In opuntia the stem is modified into a broad succulent leaf like structure that performs photosynthesis like leaves. Peepal leaf is a normal leaf that performs photosynthesis. Cacti and African euphorbias are similar in appearance, being succulent, spiny, water-storing, and adapted to desert conditions generally. But these two plants belong to different families though they share traits according to the similar environmental conditions they are placed in. Potato and sweet potato also show similar characteristics, but have different origins. Potato is a modified stem meant for storage of food. Sweet potato is a modified root also meant for the storage of food. 11

12. VESTIGIAL STRUCTURES Reduced body parts (in comparison to the same complex structure in other organisms) that have little to no function; remnant of an ancestor. Examples: Human appendix (other mammals it is necessary to aid in digestion) Human external ear muscle (useless, but still there) Human tailbone (coccyx) Wisdom teeth Goose bumps 12

13. Are There Vestigial Structures in Plants? Embryo sac of typical spermatophyte, in many cases synergids and antipodals are vestigial. In many plants three of the four megaspores disintegrate and are functionless just prior to their disappearance. In the case of higher plants, In many species stipules are reduced and functionless. Pistils in staminate flowers and stamens in pistillate flowers are vestigial. Example : Zea mays shows bisexual initials in both tassel and ear. 13

14. ADAPTIVE RADIATION Adaptive radiation is the evolutionary process by which many species originate from one species in an area and radiate to different species. First observed by Darwin in Galapagos Island. He observed finches with different types of beaks. He concluded, these finches radiated on the same island from a single ancestor Finch. All of these finches developed beaks according to the kind of food available to them. They later came to be known as Darwin’s finches . 14

15. EMBRYOLOGY 15

16. Embryology, used to help determine similarities and differences between various species. An embryo is the fertilized egg , goes through the processes of development that are specific to that species. Most embryos look similar in their early stages, but as they develop, the differences between species become more obvious. Many traits of one type of animal appear in the embryo of another type of animal. Patterns of embryological development can indicate a common ancestry. – Fish, birds, mammals & reptiles all have gills; only fish retain theirs – Fish, birds, humans & reptiles all have tails; ALL but humans retain theirs 16 Embryology

17. Vertebrae that evolved from fish pass through similar embryonic stages. A flexible notochord and somites form along each side of it. Somite will become major structures such as muscle , vertebrae, connective tissue, larger glands of body. 17 Embryology

18. Embryology in Plants The first embryo producing plants most probably from an algal ancestor around 450 mya . Many developmental features are shared between the closely related algal sisters to land plants. Green colour indicates proembryo or apical part in all embryos, grey colour indicates the foot in liver worts , hornworts, mosses and ferns and the suspensor in lycophytes, gymnosperms and angiosperms . Homeodomain transcriptional factors have been reported to play a critical role in regulating sexual development and establishing a haploid-to-diploid morphological transition during evolution . 18

19. Haeckel’s Recapitulation theory (biogenetic law) Postulated by Ernst Haeckel (1866) The theory of recapitulation, also called the biogenetic law or embryological parallelism The law expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"— It is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (ontogeny), goes through stages resembling or representing successive adult stages in the evolution of the animal’s remote ancestors (phylogeny). 19

20. Atavisms Atavisms are often seen as evidence of evolution . It is the tendency of reversion. atavism is a modification of a biological structure where by an ancestral trait reappears after having been lost through evolutionary change in previous generations. Birds lost teeth as physical structures between 60 and 80 million years ago, several studies have shown that those tissues within birds that would normally produce teeth still retain the potential to do so. 20

21. Atavism Geoffrey St. Hilaire - first scientist observed that some bird embryos exhibited evidence of tooth formation. Humans do not have tails, and Hens don’t have teeth, but they have the genes for it but only in very rare situations do these traits manifest themselves as a phenotype. This phenomenon is called atavism— the reappearance of a trait that had been lost during evolution. 21

22. PHYSIOLOGY 22

23. Physiological adaptations change phenotype by altering certain microscopic parameters. Similarities and differences between the "same“ gene in different organisms (that is, a pair of homologous genes) can help us determine how closely related the organisms are. Homologous genes Biologists often compare the sequences of related genes found in different species (often called homologous or orthologous genes) to figure out how those species are evolutionarily related to one another. This shows that they have a common ancestor . For instance, humans, cows, chickens, and chimpanzees all have a gene that encodes the hormone insulin , because this gene was already present in their last common ancestor. The more DNA differences in homologous genes between two species, the more distantly the species are related. 23

24. Evidence for evolution: Molecular biology • Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. The most basic level, all living organisms share: • The same genetic material (DNA) • The same, or highly similar, genetic codes • The same basic process of gene expression(transcription and translation) These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation 24

25. REFERENCES Hutchinson, A. C. (2005). Evolution and the Common Law. Cambridge University Press. Ingrouille , M., & Eddie, B.(2006). Plants: Diversity and Evolution. Cambridge University Press. Jill U. Adams & Kenna M. Shaw(2008). Atavism: Embryology, Development and Evolution , Nature. Knobloch W. I, Are There Vestigial Structures in Plants?( 1951), science,465. Tatyana Radoe , Prasad Vaddepalli . Evolution, Initiation and diversity in early plant Embryogenesis , Laboratory of Biochemistry, the Netherlands, 533-540. https://www.khanacademy.org/science https://www.olabs.edu.in/ 25

26. THANK YOU 26