The southern species, on the basis of this character of leaves are considered to be more primitive than the northern oaks. Microbes that divide fast have the ability to multiply and become millions of individuals within hours. If a sweat soaked dirty shirt is kept in wheat barn. You can download Free Evolution - Class 12, Biology pdf from EduRev by using search above. Lest we forget, some mammals live wholly in water. Examples - human baby born with tail etc. Oriental : Asia, South of Himalayas; India, Ceylon, Malay, Peninsula, Sumatra, Bornea, Java Celebes and Philippines.
This is because these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to penicillin drug. Therefore its all cells were of same genetic structure. Mutations are large, random and directionless while Darwinism variations are small and directional. Not only dolphins, there are certain other animals such as crow, parrot, chimpanzee, gorilla, orangutan, etc. EduRev is like a wikipedia just for education and the Evolution - Class 12, Biology images and diagram are even better than Byjus! You will learn about these in higher classes. These are either attached to white goose neck barnacles or to tan-coloured rocks.
Development of similar adaptive functional structures in unrelated groups of organisms is called convergent evolution. Another word used is fitness of the individual or population. The HbS, HbS, condition leads to the death of organism. Cosmozoic Theory — Proposed by Richter. These theories are — a Theory of special creation. This type of group of cells is known as clone. Conscious Reaction Animals with well developed nervous system react consciously to any change in environments Darwinism does not involve any conscious reaction.
Accroding to Theodosius Dobzhansky 1973 , nothing in biology makes sense except in the light of evolution. As they passed on this acquired character of elongated neck to succeeding generations, Giraffes, slowly, over the years, came to acquire long necks. The idea of natural selection striked in his mind. Changes during evolution of horse are as follows — 1. For example the proteins found in the blood of man and apes are similar. Some reproduce more and some minimum.
These features were inherited by the offspring. In this every colony is formed by the division of bacterial cells. Galaxies contain stars and clouds of dust and smoke. Louis Pasteur French 1862 — Pasteur is popular for Germ Theory of Diseases or Germ theory and he disproved abiogenesis. Organisms produce more offspring than the available food and space so that a struggle for existence ensues amongst them. Nucleoproteins were first sign of life.
Galaxies contain stars and clouds of gas and dust. Viruses Living and nonliving 2. Orohippus : It evolved in middle Eocene epoch. The universe expanded and hence, the temperature came down. There were in South America mammals resembling horse, hippopotamus, bear, rabbit, etc.
The theory is silent about it. The loss of a section of population by death an after sometime a new species is formed that effect is known as Bottleneck effect. It is also believed that each era of earth's history started with a revolution or cataclysm and ended with yet another revoluation. Small sized reptiles of that era still exist today. Important Point : Palaeontological and Biogeographical evidences are considered as best evidences in support of organic evolution. By studying fossils following facts about organic evolution are evident — 1. Apes like characters : — Less cranial capacity — 400 — 500 c.
In this experiment Miller took the mixture of methane, ammonia and hydrogen ratio 2 : 1 : 2 in a large flask and passed steam over it by boiling water and connecting it with a glass tube. Protoplasm : Structure and chemical composition of protoplasm is same from protozoa to mammalia. Hence, the resistant bacteria multiplied quickly as compared to non- resistant sensitive bacteria, thereby increasing their number. This is called convergent evolution. He observed that maggots developed only in the uncovered jar while maggots could not develop in the meat in closed jars. The theory that first form of life arose slowly through evolutionary forces from non-living molecules is called biogenesis.
Aquatic birds stretched their toes and developed web. Selection pressure acting from within the population as a result increased competition may push the phenotype away from the population mean towards the extremes of the population. These, therefore, will survive more and hence are selected by nature. From the original seed-eating features, many other forms with altered beaks arose, enabling them to become insectivorous and vegetarian finches Figure 7. When the earth's surface cooled down and its temperature decreased to 100°C, water formed on it.
Fish with stout and strong fins could move on land and go back to water. In plants, the pollen coming from a different species may be rejected by the stigma. This is due to similar habitat that resulted in similar adaptive features in different groups of organisms. Directional selection removes more individuals from one end of the normal curve of variability distribution and adds towards the other end and alters the mean value of the trait in the population in a particular direction. The study showed that different form varied over time and certain life forms are restricted geological time span. He bred two individuals differing in certain well-defined characters, and observed the ratio in which various contrasting parental characters appeared in successive generations. Jawless fish probably evolved around 350 mya.