Today we will see how to make project on ' project on evolution' this project is only for class 12th student and this project is belongs to 'Biology' in this project we will see how can we make this project .
THE THEORY OF EVOLUTION
Evolution as a theory suggests that the great variety of plant and animal life on earth developed gradually through natural processes.
Although such an idea had been suggested as early as the sixteenth century, the great English biologist Charles Darwin (1809-1882) gave the theory prominence.
The most important of Darwin’s works is On the Origin of Species by means of Natural Selection, first published in 1859.
Darwin’s examination of geological formations, collection of fossils, and study of plants and animals from 1931 to 1936 led him to doubt that divine creation had brought all species of living things into existence at one moment. His doubts challenged the traditional theory of creationism held for centuries in the western world.
NATURAL SELECTION
Darwin’s theory was based on the idea that species changed or adapted over time in response to their environment.
He based his theory on his observations that members of a single species vary greatly in shape, size, colour, and strength. Most of these variations, he believed, could be inherited.
He also noticed that the population of a species tended to remain the same size, even though parents usually produced more than two offspring He concluded, therefore, that there had to be competition for survival. In the struggle for survival, his theory stated, organisms with characteristics less suited to their environments likely died without producing young. Those organisms with more useful characteristics survived and reproduced, passing on these variations to their offspring As other descendants developed other favourable variations, they passed on these characteristics as well.
As a result, Darwin argued, organisms with more helpful characteristics survived the struggle for existence. Others died out. He called this process Natural Selection.
First, the science of genetics has helped to explain the variations in each species and how these variations are passed on.
Second, evidence gathered from fossil remains in recent years supports Darwin’s ideas.
Gaps in the theory still remain, however, and we do not have a complete record of human evolution.
The physical evolution of humans
Evolution traces human development through several stages or species from the first humanlike beings to modern humans. Although we still do not know exactly when the evolution of humans and apes diverged or who our common ancestor is, we do know that hominids (humanlike creatures) began to appear over four million years ago.
Hominids are distinguished from apes most notably by their bipedalism (their ability to walk on two feet) and by their larger brain size. All hominids are members of the human family tree.
What is a Hominid?
• Modern humans & our direct and indirect ancestors after our lineage split from the chimpanzee
• Until recently, earliest hominids were dated between
3.5 and 2.4 mya & placed in the genus Australopithecus
• In last few years, time range of Australopithecus pushed back to 4.2 mya, distribution expanded to include regions outside E. and S. Africa
• New finds from 4.5-7 mya are thought to be hominids that predate Australopithecines, although their status is debated
HOMINID SITES
🔹 Earliest fossil hominid sites are in Africa
🔹 They now span the latest Miocene to the early Pleistocene from about 6-7mya to about 1.6mya
🔹 The major groups of sites are:
1. Ethiopia = Middle Awash valley & Hadar (Australopithecus afarensis)
2. Kenya = Lake Turkana
3. Tanzania = Olduvai Gorge
4. South Africa = various sites in limestone caverns centered around Sterkfontein
WHY DID BIPEDALISM BECOME THE PRIMARY ADAPTATION OF HUMIND
1 Carrying behavior
2 Reduction of overall heat stress - facilitates heat loss through convection by exposing body to air currents, only humans have sweat glands that produce moisture to cool body
3 Most energy efficient way to travel long distances
4 Allows for better vision in open environments & defensive action against predators by freeing hands to throw objects
WHAT ARE PREMATES
Primates are difficult to characterize as an order
› they lack the strong specializations found in
most other mammalian orders
We can, however, point to several trends in their evolution that help define primates and are related to their arboreal, or tree-dwelling, ancestry
TRENDS IN PRIMATES
1 These include changes in the skeleton
› and mode of locomotion
› an increase in brain size
› a shift toward smaller, fewer and less
specialized teeth,
› and the evolution of stereoscopic vision
› and a grasping hand with opposable thumb
2 Not all these trends took place in every primate group nor did they evolve at the same rate in each group
Classification of Primates
The primate order is divided into two suborders:
1 Prosimians, or lower primates
› include the lemurs, lorises, tarsiers, and
tree shrews,
2 Anthropoids, or higher primates,
› include monkeys, apes, and humans
ARDIPITHECUS RAMIDUS
Our understanding of human evolution is constantly changing. New and different species are found and the human evolutionary tree grows more branches.
One example of continuous change came in 1994 at Aramis, Ethiopia, where people unearthed fossils of a previously unknown species dating from 4.4 million years ago. This humanlike creature walked the earth nearly half a million years earlier than the oldest human ancestor identified to that point.
This exciting discovery led to the identification of a new genus called Ardipithecus Ramidus. Ramidus has may chimplike as well as human features, but its position on the human family tree is still not certain. It is a mystery that still
has to be solved.
THE AUSTRALOPITHECINES
Australopithecus Anamensis
In 1995, Maeve Leaky of the National Museums of Kenya discovered some of the oldest representatives of a widely studied human genus, the australopithecines. She and her team located pieces of a bipedal hominid, 4.1 million years old, which she named Australopithecus Anamensis. It is an early species with very pronounced apelike teeth. Some scientists suggest that this species may have given rise to Australopithecus Afarensis.
Australopithecus Afarensis
In 1974, at Hadar, Ethiopia, Donald Johanson and his team unearthed a set of fossilized bones of a female hominid approximately 3.18 million
years old. They nicknamed their discovery “Lucy”. These fossilized bones led to the identification, in 1978, of Australopithecus Afarensis, a species that may have survived almost unchanged for 900,000 years. In Lucy’s species, Johanson believed that he had found the earliest common ancestor of all later hominids. This changed with the Aramis find in 1994, and the Leaky find in 1995.
Australopithecus Africanus
Another branch of the Australopithecus family is the Australopithecus Africanus, which lived in the southern part of Africa approximately 2.5 to 3 million years of age. There are two Africanus “off” lines, Australopithecus robustus and boisei
REPLACEMENT MODEL
1 Debate still surrounds the transition from H. erectus to our own species, Homo sapiens
› Paleoanthropologists are split into two camps
2 On the one side are those who support
› the "out of Africa" view
3 According to this camp, early modern humans evolved from a single woman in Africa, whose offspring then migrated from Africa, perhaps as recently as 100,000 years ago and populated Europe and Asia, driving the earlier hominid
populations to extinction
THE MULTIREGIONAL VIEW
1 On the other side are those supporting the "multiregional" view
2 According to this hypothesis, early modern humans did not have an isolated origin in Africa, but rather established separate populations throughout Eurasia (H. erectus > H. neanderthalenis > H. sapiens
3 Occasional contact and interbreeding between these populations enabled our species to maintain its overall cohesiveness, while still preserving the regional differences in people we see today
4 Beginning in the 1980's, Rebecca Cann, at the
University of California, argued that the geographic region in which modern people have lived the longest should have the greatest amount of genetic diversity today.
5 Through comparisons of mitochondrial DNA sequences from living people throughout the world, she concluded that Africa has the greatest genetic diversity and, therefore, must be the homeland of all modern humans.
6 Assuming a specific, constant rate of mutation, she further concluded that the common ancestor of modern people was a woman living about 200,000 years ago in Africa.
7 This supposed predecessor was dubbed "mitochondrial Eve“
8 More recent genetic research at the University of Chicago and Yale University lends support to the replacement model.
9 It has shown that variations in the DNA of the Y chromosome and chromosome 12 also have the greatest diversity among Africans today.
10 Critics of the genetic argument for the
replacement model also point out that the rate of mutation used for the "molecular clock" is not necessarily constant, which makes the 200,000 year date for "mitochondrial Eve"
unreliable.
11 The rate of inheritable mutations for a species
or a population can vary due to a number of factors including generation time, the efficiency of DNA repair within cells, ambient temperature, and varying amounts of natural environmental mutagens.
12 Further criticism of the genetic argument for the replacement model has come from geneticists at Oxford University.
13 They found that the human beta-globin gene
is widely distributed in Asia but not in Africa. Since this gene is thought to have originated more than 200,000 years ago, it undercuts the claim that an African population of modern Homo sapiens replaced East Asian archaic humans less than 60,000 years ago.
14 Similarly, it is claimed that some Chinese facial characteristics can be seen in an Asian archaic human fossil from Jinniushan dating to 200,000 years ago.
15 Like Homo erectus, East Asians today commonly have shovel-shaped incisors while Africans and Europeans rarely do.
16 This supports the contention of direct genetic
links between Asian Homo erectus and modern Asians.
THE STONE AGE
The descendants of the australopithecines lived in the period called the Stone Age. We call the period this because most of the artifacts found from this time are mad of stone. Humans who lived in the Stone Age are generally classified into a group or genus called Homo (“man”).
Most experts divide the Stone Age into three stages: Paleolithic or Old Stone Age (2 million BCE-10 000 BCE) Mesolithic or Middle Stone Age (10 000 BCE-8000 BCE) Neolithic or New Stone Age (8000 BCE-5000 BCE)
Homo Sapiens
The species name, Homo Sapiens, means “man who thinks”-an appropriate title for the species that formulated the spoken language and developed more sophisticated tools. The most ancient find was discovered in Hungary in 1965, dating from about 450 000 to 400 000 years ago. Other remains of Homo Sapiens have been found in England, Germany, and France. These bones date from approximately 250000 years ago, the period between the third and fourth ice ages. There are two types of Homo Sapiens; the Neanderthals, or Homo Neanderthalis, and Modern Human, or Homo Sapiens Sapiens.
Homo Habilis
Historians believe Homo Habilis, or “handy man”, flourished in Africa about 2.5 millions year ago. Homo Habilis were the first hominids to develop and use stone tools-proof of their ingenuity and creative ability. The brain size
and presence of humanlike teeth from fossil finds suggest that Homo Habilis might have been our human ancestor. Many scientists believe that Habilis bridges the evolutionary gap between Australopithecus and Homo. Yet, the sequence of human ascent is still uncertain. Signs of co-existence have arisen.
Homo Erectus
Homo Erectus first appeared about 2 million years ago. Their species name refers to the fact that they could walk completely upright, like modern humans. Only a few dozen skulls of
this species have been found, notably in Africa, Java, and China. The first specimens were found in Java in 1891 and 1892. Called Java Man, they are about 700 000 years old. Homo Erectus was the first species to use fire and the first to migrate into Europe and Asia from Africa.
Homo Heidelbergensis
Homo Heidelbergensis lived approximately 500000 years ago. It is often referred to as Archaic Homo Sapiens because it combines features of Homo Erectus with more modern features. The first specimen was found in a Quarry in Germany in 1907. But other specimens have been found in a variety of places around the world including, Zambia, Southern Africa, Tanzania, and parts of Northern Europe as far North as England.
Many researchers consider Homo Heidelbergensis a possible ancestor for both
modern humans (Homo Sapiens) and Neanderthals (Homo Neanderthalensis), while others are still not comfortable with this label.
Neanderthals
Located in Europe, Neanderthals first appeared
about 230 000 years ago and disappeared approximately 30 000 years ago. Quarry workers in Dusseldorf first discovered the remains of these people in the Neander Valley of German in 1856. More finds have since been located primarily in Belgium, France, and other parts of Europe. They traveled as far as China and the Middle East. Their total population at any one time probably numbered fewer than 100000.
It is still unclear who the Neanderthals were, scientists wonder whether they were our direct ancestor or whether they were a separate species. It is commonly held, however, that the Neanderthals were driven to extinction by
modern humans.
THE MODERN HUMAN
About 40 000 years ago, modern humans moved into Europe armed with the skills to make clothing, better shelters, and more efficient hearths. Nineteenth-century scientists named these newcomers Cro-Magnon people after the French rock-shelter where three anatomically modern skeletons were discovered in 1868.
Cro-Magnons were Homo Sapiens who evolved in Africa and slowly pushed their way into Europe. They developed the ability to endure colder climates, even climates as cold as those found in Iceland or Greenland. Cro-Magnon people were about as tall as modern northwestern Europeans. They also had many of the same facial and cranial features as modern northwestern Europeans. Eventually, their successors moved into Asia. About 30 000 years ago, they crossed the Bering Strait after the retreat of the ice and entered the Americas. Others reached Australia. With this migration, our modern human ancestors spread throughout the world.
ARE WE STILL EVOLVING
Microevolution: change in gene frequency – YES Macro evolution : formation of species – NO Are we genetically different from our Homo sapiens ancestors who lived 10-20,000 years ago? The answer is almost certainly yes. In fact, it is very likely that the rate of evolution for our species has continuously accelerated since the end of the last ice age, roughly 10,000 years ago.
This is mostly due to the fact that our human population has explosively grown and moved into new kinds of environments, including cities, where we have been subject to new natural selection pressures.
For instance, our larger and denser Populations have made it far easier for contagious diseases, such as tuberculosis, small pox, the plague, and influenza to rapidly spread through communities and wreak havoc. This has exerted strong selection for individuals who were fortunate to have immune systems that allowed them to survive.
There also has been a marked change in diet for most people since the end of the last ice age. It is now less varied and predominantly vegetarian around the globe with a heavy
dependence on foods made from cereal grains. It is likely that the human species has been able to adapt to these and other new environmental pressures because it has acquired a steadily greater genetic diversity. A larger population naturally has more mutations adding variation to its gene pool simply because there are more people. This happens even if the mutation rate per person remains the same. However, the mutation rate may have actually increased because we have been exposed to new kinds of manmade environmental pollution that can cause additional mutations.
It is not clear what all of the consequences of the environmental and behavioral changes for humans have been. However, it does appear that the average human body size has become somewhat shorter over the last
10,000 years, and we have acquired widespread immunity to the more severe effects of some diseases such as measles
and influenza.
THE FUTURE
⚫ It remains to be seen
› how we will use this technology in the future
› and whether we will continue as a species,
› evolve into another species,
› or become extinct as many groups have before Us
YOU CAN WATCH OUR VIDEO
you can see our pdf also
DOWNLOAD PDF --- click here
0 Comments