1. A region's climate is generated by five components: atmosphere, hydrosphere, cryosphere, geosphere, and biosphere. The oceans provide barriers to dispersal which help explain the existence of zoogeographical realms. 2. Around 250 million years ago, all the oceans were connected as the supercontinent Pangaea existed. Continental drift and the breakup of Pangaea over time are what led to the formation of different zoogeographical realms. 3. The Cretaceous–Tertiary extinction event around 66 million years ago saw the demise of the dinosaurs and many other species. It was likely caused by large-scale volcanism, marine regression, and an

1. Melaku Tefera, College of Veterinary Medicine, Haramaya University, P.O.Box 144 Haramaya Campus.
Ethiopia. 251-0914722459, <melaku22@yahoo.com>
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2. A region's climate is generated by the climate system, which has five
components: atmosphere, hydrosphere, cryosphere, geosphere, and biosphere
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The primary role of oceans in all this is in providing barriers to dispersal
Continental drift and the unique time-sequence of lineage origination, then, are
what explain the existence of what we call the zoogeographical realms.
About 250mya all the ocean were one
Pangaea and Continental drift

3. Photos/Illustration: National Park Service, Randal Irmis, Gautam Rangan, Randal Irmis/Andrew
Lee/Nick Pyenson
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4. Cretaceous–Tertiary extinction event
Cretaceous–Paleogene (or K–Pg) extinction
K–T extinction event, it is associated with a geological signature known variously as the k-T boundary , the Cretaceous–
Paleogene boundary or the K–Pg boundary, usually a thin band of sedimentation visible wherever rocks of this age are
exposed
volcanism, marine regression
and extraterrestrial impact
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Timeline of mass extinction events. The five named vertical bars indicate mass extinction events. Black
rectangles (drawn to scale) represent global reef gaps and brick-pattern shapes show times of prolific reef
growth (Veron ,2008)
Global drop in sea level Deep-ocean anoxia Glaciation? Depletion of oxygen in marine waters
Phanerozoic

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7. 72.6 billion cubic meters per year Renewable groundwater
122 billion cubic meters per year

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10. Lake Altitude
(m)
Area
(km²)
Mean depth (m) Crocodiles
Rift Valley
Chamo 1 280 550 13.0 +
Abaya 1 285 1 160 7.1 +
Awassa 1 710 90 11.6 -
Shala 1 570 410 8.6 +
Langano 1 585 230 17.0 -
Abijata 1 575 205 7.6 +
Ziway 1 850 435 2.5 -
Koka* na 255 9.0 +
Other areas
Tana 1 830 3 500 8.0 ±
Fincha* 2 160 170 9.0 -
Hashenge - 7 005 -
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11. Heavy hunting for skins began in the mid-
1950s. In 1963 the French owned, Dofan
Ethiopia Share Company had crocodile
hunting concessions on several rivers and
in 1966 Dofan established Modjo tannery
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12. By 1971 Nile crocodile were seriously
depleted.
Subsequently, in 1972 commercial hunting of
crocodiles was prohibited in Ethiopia
Ethiopia joined the Convention on International Trade in
Endangered Species (CITES) which regulates trade in
crocodile products, in 1988 and the Nile crocodile was
transferred from Appendix I, the highest order of protection,
to Appendix II to allow an export quota for ranched skins.
The initial quotas approved by CITES were from 9,000 to
12,000 skins per year for export based on the ranching
programme, though total skin sales since 1984 were less
than 8,300.
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13. 1980-The crocodile ranch in Arba-Minch is
built on the edge of Lake Abaya, in Ethiopia's
southern Rift Valley, and is home to around
4,000 of the reptiles
Year No. Nests No. Eggs Average clutch
size
Hatched Hatchlings to
ranch
Hatchlings
released
1985 4 129 32 72 72 Nil
1986 72 3176 44 2713 2713 Nil
1987 206 5521 27 4928 2622 2306
1988 132 4103 31 3510 2587 923
1990 265 7752 29 6244 6045 199
1991 74 2749 37 2121 2005 116
1997 242 5663 23 4011 4011 Nil
2001 58 2572 47 2120 2000 120
2004 262 11840 45 9400 8000 1400
Total 1607 53124 42755 37195 5559
Table. Egg collection data. Arbaminch crocodile ranch
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16. Country 2003 2004 2005 2006 2007 2008 2009 2010
Botswana 0 0 0 0 *320 *374 *1,626 *1,500
Brazil 1 44 0 0 0 0 0 0
Ethiopia 900 300 347 727 *594 492 0 4
Israel 0 0 0 0 0 0 *2 0
Kenya *1,687 2,850 9,550 8,710 6,354 4,504 4,283 4,309
Madagascar 7,300 4,760 4,850 6,660 5,500 2,640 2,450 0
Malawi 301 *100 *1,038 698 *1,350 3,370 2,603 *500
Mali 0 0 0 0 0 107 0 0
Mauritius 118 400 150 184 231 189 100 0
Mozambique 3,160 0 1,156 2,000 179 566 0 2,449
Namibia 0 0 400 305 0 0 600 2
South Africa 31,321 35,760 35,486 34,203 36,014 44,697 25,050 47,267
Uganda 600 600 *600 *300 0 *290 0 *500
Tanzania *1,439 *1,067 *1,584 *1,100 *1,556 *1,784 1,365 601
Zambia 28,019 26,353 *33,184 *42,266 *44,597 28,197 43,655 23,717
Zimbabwe® 73,707 68,263 63,146 71,616 64,490 81,554 67,350 80,995
Total 148,553 140,497 151,491 168,769 161,185 168,764 149,082 161,840
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21. •Temperature regulation is a dynamic process
that involves behavioral and physiological
adjustments.
•The consequences of devoting time to
thermoregulation have broad behavioral and
ecological significance. The time spent in
thermoregulation can sometimes reduce the
time available for other important activities
(Huey, 1982). Climatic conditions, social
interactions Land water movement is
triggered by - Circadian rhythm
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22. Lack of thorough scientific study, combined with a misunderstanding of this species, remains
the biggest threat to Nile crocodiles
Habitat loss
fragmentation of natural habitats .The loss of swamps, marshes, wetlands and other natural
systems into agriculture, mines, and urban developments, the draining of swamps and other
wetlands, Dam construction
Hunting and exploitation
Persecution and trophy hunting
People have long considered crocodiles vermin or a dangerous nuisance. For this reason,
crocodiles have been hunted to extinction in some places
Conflict with humans
presents perhaps the greatest threat to the Nile crocodile. As large and potentially
dangerous predators, people are often, understandably, intolerant of crocodiles, and
deliberate destruction of nests and killing of adults is common . Crocodiles may also come
into conflict with fishermen, damaging nets when trying to remove fish from them
Pollution
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25. By focusing narrowly on economic incentives,
conservationists
risk undermining their credibility and
obscuring other valid reasons to protect
nature.
Education
Cultural and intrinsic values, respect for nature,
interest in wildlife ecology and pride in the
occurrence and conservation of a rare and iconic
species can also form a strong motivation
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