ZOO503 Final Term Current Papers by Amaan Khan

ZOO503 - Zoogeography and Paleontology · 1. · Biogeography of South America: 10 · South America

The history of the biota of South America has been dominated by the effects of the great earth‐ engine of plate tectonics. Some of these effects were caused by the

westward drift of the continent, which led to mountain building and consequent climatic changes, but most were the result of changes in its relationship with North America. As noted in the description of the origin of the Caribbean islands in the ‘The West Indies’ section, there had been islands in that region ever since the Americas started to move westward in the Early Cretaceous. This may have been the route by which some North American dinosaurs dispersed southward in the Mid‐Cretaceous,

accompanied by some early types of marsupial and placental mammal. But this connection has always been tenuous, sometimes permitting passage and sometimes becoming broken. This led to cycles of immigration, isolation and evolution, and final new immigration and extinction.

The Early Cenozoic

The mammal fauna of South America today is characterized by a few marsupials (opossums) and a diversity of edentate placental mammals known as the Xenarthra (sloths, armadillos and South American anteaters) that are hardly known elsewhere. However, in the Late Cretaceous, South America had a mammal fauna of strange marsupials and of ungulate placentals quite unlike anything known elsewhere in the world. Alfred Wallace, one of the founders of zoogeography noted that the range boundaries of Amazonian birds seemed to coincide with the pattern of the rivers. It is fascinating that recent research shows that closely related taxa of some birds are to be found on either side of rivers throughout Amazonia.

2. What are three types of radiated amniotes 5

These three skull patterns diagnose the key clades among amniotes which are

1)

The anapsid (“no arch”) is the primitive state skull pattern, since there are no temporal openings. The Anapsida include various early forms such as Hylonomus, as well as some Permian and Triassic reptiles, and the turtles. The two other skull patterns seen in amniotes are

2)

The synapsid (“same arch”), where there is a lower temporal opening. The Synapsida include the “mammal-like reptiles” and the mammals.

3)

The diapsid (“two arch”) pattern, where there are two temporal openings. The Diapsida includes a number of early groups, as well as the lizards and snakes and the crocodiles, pterosaurs, dinosaurs and birds. .

Q3. When modern birds appear? (2 marks)

Modern groups of birds appeared in the latest Cretaceous and Early Tertiary, including flightless ratites and ancestors of water birds, penguins and birds of prey. The perching birds or songbirds, consisting of 5000 species today, radiated in the Miocene

Q4. What is Kleptoparasitisim with example? (5 marks)

Kleptoparasitism (literally, parasitism by theft) is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food (as in the case of cuckoo bees, which lay their eggs on the pollen masses made by other bees; food resources could also be in the form of hosts of parasitic or parasitoid wasps). The term is also used to describe the stealing of nest material or other inanimate objects from one animal by another. One very widespread duck in both continents is the gadwall. It feeds mainly on submerged vegetation, which is most abundant in nutrient‐ rich (eutrophic) waters. It cannot dive, so it

feeds by upending, and this generally restricts it to the shallow parts of a lake, where it may encounter some competition from other water birds, such as the mallard. Coots (both Eurasian coot and the American coot dive for their food and bring vegetable matter to the surface from greater depths. The coots are messy eaters, and it is not difficult for gadwall to move in and collect some of the loot. This behavior is called kleptoparasitism, and it is an effective way of widening the niche of the gadwall.

5. Write a note on geographical history of New Caledonia

New Caledonia

Geological studies show that New Caledonia is the smallest (about 1600 km2) surviving fragment of Gondwana, having rifted away from Australia in the Late Cretaceous 80–65 mya and reaching its present position 1500 km east of it 50 mya. It is a hotspot for diversity: 77% of its flowering plant species are endemic to the island, as are 98% of the species of the flowering plant family Sapotaceae. In view of the large amount of research that shows the frequency of long‐ distance dispersal in

such scenarios, most biogeographers today believe that this was the mechanism of arrival of the ancestors of the New Caledonian taxa. Geological studies show that the island was submerged for long periods in the Paleocene– Eocene, so that the island was not available for colonization until about 37 mya. The New Caledonian species must therefore have diverged from their ancestors after this date. Panbiogeographers, however, reject long‐ distance dispersal. They therefore have to theorize that the

Cretaceous ancestors of the present biota were widespread across the Pacific islands, including on supposedly formerly exposed large plateaux such as the Ontong Java plateau.

Biogeographers in Sweden and France have investigated the history of the New Caledonian species of the angiosperm family Sapotaceae. They found that these resulted from nine separate colonizations of the island between 33 and 4.2 mya, dates that are about 40 million years after the rifting of New Caledonia from Australia. New Guinea and Australia were the most important sources of the arrivals, those from Pacific islands arriving only more recently, 27–24 mya. These results are clearly totally incompatible with the panbiogeographers’ theories.

6. History of old world tropical mammal fauna of Africa 5

Africa contains the best known and most distinctive of the Old World tropical mammal fauna. Molecular studies of the interrelationships of the different orders of placentals suggest that the common ancestor of a group of African placentals entered the continent in the Late Cretaceous. This group is made up of the elephants, hyracoids (conies), aquatic sirenians (sea cows), elephant shrews, aardvarks, Cape golden moles, insectivorous tenrecs and extinct embrithopods; they have been placed together in a super order, Afrotheria, that is endemic to Africa. The early horse Hipparion, which had evolved in North America, appeared in both Eurasia and Africa, while rhinoceros, hyenas and sabre‐ toothed cats dispersed from Africa to Eurasia. The elephants

originated in Africa in the Eocene, migrated into Eurasia in the Early Miocene and migrated back later in the Miocene. The ancestors of the mammoths and modern Asian elephant probably evolved in Africa 4 to 5 mya and migrated back into Eurasia 2 million years later.

Q7. Name the three amniotic layers in embryo and write their functions. (3 marks)

•  Enclose the embryo (the amnion)
•  Collect waste (the allantois)
•  line the eggshell (the chorion)
•  Yolk, a yellow material rich in protein

Q8. Difference between Sympatry and Allopatry . (3 marks)

Sympatry

An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation. Darwin's finches and their beak sizes

Allopatric speciation

Also referred to as geographic speciation, is a mode of speciation that occurs when biological populations of the same species become isolated from each other.

Q9. What is Redundant species hypothesis? (3 marks)

According to the redundant species hypothesis, the removal of certain species from an ecosystem would have little or no effect on the functioning of that ecosystem. Here, the function of an ecosystem could refer to its overall productivity, its rate of nutrient cycling or its general self‐ sustainability.

Q10. What is meant by Biogeography? (2 marks)

Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time.

Q11. What is meant by Niche? (3 marks)

The demands that an organism places on its environment in terms of physical and chemical conditions, space and food supply help to define what ecologists call its niche. But the concept of the niche goes beyond the basic physics and chemistry of its habitat and covers all aspects of how the organism makes a living. It includes the food an animal requires, but also encompasses the way in which it acquires that food. The kestrel is a bird that hunts small mammals by day, whereas an owl performs a similar