Cormorant fishing (Ukai)
6) 신경계 및 감각기관
Nervous system and migration of birds
The nervous system is large relative to the bird's size. The most developed part of the brain is the one that controls the flight-related functions, while the cerebellum coordinates movement and the cerebrum controls behaviour patterns, navigation, mating and nest building.
Most birds have a poor sense of smell with notable exceptions including kiwis, New World vultures and tubenoses.
The avian visual system is usually highly developed.
Birds possess ultraviolet (UV) sensitive cone cells in the eye as well as green, red and blue ones. This allows them to perceive ultraviolet light, which is involved in courtship.
The eyelids of a bird are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third eyelid that moves horizontally. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds.
Most birds cannot move their eyes, although there are exceptions, such as the Great Cormorant.
The avian ear lacks external pinnae but is covered by feathers.
A few species are able to use chemical defenses against predators; some birds can eject an unpleasant oil against an aggressor, and some species have a powerful neurotoxin in their skin and feathers.
Many bird species migrate to take advantage of global differences of seasonal temperatures, therefore optimising availability of food sources and breeding habitat. These migrations vary among the different groups.
The ability of birds to return to precise locations across vast distances has been known for some time. Birds navigate during migration using a variety of methods. For diurnal migrants, the sun is used to navigate by day, and a stellar compass is used at night by internal clock.
A mystery disease is killing penguins in Antarctica.
Australian scientists have found over 100 penguins dead near their Mawson base.
They fear there could be many more. It is not unusual to find one or two dead penguins in a colony, but this kind of large-scale mortality is rare. The scientists fear an unknown disease is responsible and are concerned that it could spread.
They have restricted human access to the penguins.
They are also disinfecting boots and clothing after leaving the area. Blood and tissue samples are being taken from the birds and will be sent by ship for analysis in Australia in the next few days. The penguins affected are called Adelie penguins (Pygoscelis adeliae) and they are among the most abundant of all the penguins in the Antarctic, so the species is under no imminent threat.
There are about 15,000 in the Australian colonies at Mawson and over two million worldwide. But their numbers have been declining here in Antarctica and it is thought that climate change may be to blame.
They are losing some of the ice that is their natural habitat. Keith Reid, an expert in penguins at the British Antarctic Survey, says there is no cause for immediate alarm at the disease outbreak. "The Australians are very concerned about the potential for humans introducing disease into penguin colonies. But if this was an externally introduced disease, it would go through a colony extremely rapidly."
He said one possibility was that skuas (Antarctic seabirds) travelling large distances while scavenging around the oceans could introduce disease into a penguin colony.
It has also been a bad year for the thousands of Emperor penguins living near the British base at Halley.
The ice broke up early this year, before the chicks were old enough to fend for themselves. And it is thought that most of them have drowned or died of hypothermia.
5. 수생포유류
1) 외부형태 및 골격계
(1) 수생포유류는 물범류(Phocidae ; true seals), 물개류
(Otariidae ; eared seals), 그리고 해마류(Odobenidae ;
walruses)가 속하는 기각류(pinnipeds), 고래(whales)와 돌고 래(dolphins와 porpoise)가 속하는 고래류(cetaceans), 해우 (manatee ;
Trichechus
spp.)와 듀공(dugong ;Dugong
dugon
)이 속하는 해우류(sirenians), 그리고 해달(sea otter ;Enhydra lutris
)과 북극곰(polar bear ;Ursus maritimus
) 등 이 있다.Pinnipeds (from Latin pinna, wing or fin, and ped-, foot) or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae (the walrus ; 바 다코끼리), Otariidae (eared seals, including sea lions and fur seals ; 바다사자 와 물개), and Phocidae (earless seals, common seal ; 바다표범).
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's Dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 LT; 11 ST) (the Orca or Killer Whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The family
Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about ten million years ago, during the Miocene. Dolphins are considered to be amongst the most intelligent of animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
Porpoises(쇠물돼지) are small cetaceans of the family Phocoenidae; they are related to whales and dolphins.
They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen. The most obvious visible difference between the two groups is that porpoises have flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and shorter beaks.
The Blue Whale (흰긴수염고래 ; Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). At up to 32.9 metres (108 feet) in length and 172 metric tonnes (190 short tons) or more in weight, it is the largest animal ever to have existed
Sirenia (commonly referred to as sea cows) is an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. Four species are living, in two families and genera. These are the dugong (1 species) and manatees (3 species excluding a possible fourth species, the Dwarf Manatee).
Sirenia also includes Steller's sea cow, extinct since the 18th century, and a number of taxa known only from fossils. The order evolved during the Eocene, more than 50 million years ago.
Sirenia, commonly sirenians, are also referred to by the common name sirens, deriving from the sirens of Greek mythology. This comes from an urban legend about their discovery, involving lonely sailors mistaking them for mermaids.
(2) 가슴과 배 사이에 근육성의 가로막(횡격막)이 있다. 피부는 털로 덮여 있다.
(3) 목은 일반적으로 굵고 짧으며, 고래의 경우 경추는 서로 융 합되어 목을 움직이지 못한다. 꼬리는 수평으로 뻗은 지느러 미(fluke) 형태로 상하운동으로 유영한다.
(4) 앞다리는 가슴지느러미로 변하였으며, 지느러미 속에는 다 섯 개의 발가락 골격을 가지고 있다.
(5) 뒷다리가 없으며, 고래의 경우 흔적기관(vestigial
structure)인 골반(pelvis)을 가진다. 그리고 수염고래나 향유고래(sperm whale ;
Physeter macrocephalus
)의 경 우 퇴화된 뒷다리(rudimentary hind limb)를 가진다.(6) 고래의 경우 등의 피부가 볼록하게 솟아 생긴 등지느러미 (dorsal fin)를 갖는다.
○
The body is fusiform. The forelimbs, also called flippers, are paddle-shaped. The end of the tail holds the fluke, or tail fins, which provide propulsion by vertical movement. Although whales generally do not possess hind limbs, some whales (such as sperm whales and baleen whales) sometimes have rudimentary hind limbs; some even with feet and digits. Most species of whale bear a fin on their backs known as a dorsal fin.
The neck vertebrae are fused in most whales, which provide stability during swimming at the expense of flexibility. They have a pelvis bone, which is a vestigial structure.
흔적기관으로 일컬어지는 뼈로는 고래의 골반 뼈가 있다. 다른 동물의 골반 뼈가 발견되는 부분에 이 뼈가 위치해 있다. 이 뼈는 흔적기관으로 불린다. Awbrey (1983)는 고래의 골 반 뼈에 관한 진화론적 논쟁을 요약하였다.
“고래류는 흔적기관의 예를 갖고 있다. 골반은 작아졌고 더 이상 뒷다리를 척추와 연결 짓 지 않는다. 두 개의 작은 뼈는 생식과 배변 근육을 지지하는 기능을 할 뿐이다. 그 사실은 설 계 혹은 진화 중 그 어느 것에도 적합할 수 있다.”
그는 그 문장을 정당화하기를 고래들이 때때로 비정상적인 다리뼈를 만들기도 하기 때문에 오직 진화론자들만이 줄어든 골반 뼈와 다리뼈의
흔적에 대해 가장 잘 들어맞는(parsimonious) 설명을 제공할 수 있다고 하였다.
여러 연구자들은 실제로 이 뼈들이 그 내부기관을 지지하며, 여러 근육을 위한 접촉점으로 사용된다 는 것을 발견해 왔다. 특히 골반은 생식기 근육의 부착점으로 사용되며, 여러 고래의 경우 그러한 사 례가 확인되었다.
* 고래의 흔적기관(골반뼈) *