最近一直在生物老師圈子炒得沸沸騰騰的,
剛翻了一下campbell和一些資料,
campbell裡面的定義寫著


oviparous (卵生)
Referring to a type of development in which young hatch from eggs laid outside the mother’s body.

ovoviviparous (卵胎生)
Referring to a type of development in which young hatch from eggs that are retained in the mother’s uterus.

viviparous (胎生)
Referring to a type of development in which the young are born alive after having been nourished in the uterus by blood from the placenta.


在高國中教學上,以往教授卵胎生是一件很正常的事情
由於有學者老師有意見,似乎就這樣被拿掉了。


當然在生物這門學問上,一直後面的資訊推翻前面,
一件很正常的事情,但事實真的是如此嗎?




教科書在三四年前開始有刪除卵胎生這個名詞的說法
官方做了這個說明

1970年爬蟲類動物學者首先捨棄卵胎生的用詞,
因為在爬蟲類動物中,胎生和卵生的區分界線並不明顯,
他們認為這是一種連續性的演化行為,

卵胎生的動物仍然可以接觸到母體所提供的養分(但機制不明),
故有學者建議刪除卵胎生一詞。


他們曾經將特定標定的電解質,注入沒有明顯的母體提供養分的構造的母體,
結果胚胎裡面就偵測到這個物質了,表示母體能將物質傳給胚胎。

所以目前在爬蟲類

卵生的定義:指卵被產出後幾禮拜~數月,幼體才孵化的;

胎生的定義:胚胎在母體發育完全後才被產出者。
有的發育完全但包在薄膜內數天才出來的,
或一出來就可以自由活動的,都屬於胎生。



campbell 在介紹爬蟲類上面也出現了這段文字

Many species of snakes and lizards are viviparous; in such species,
the extraembryonic membranes form a kind of placenta
that enables the embryo to obtain nutrients from its mother.

在爬蟲類並沒有提及卵胎生的名詞,而是介紹了會有類似胎盤的構造出現。















不過,在介紹鯊魚時就開始出現卵生、卵胎生以及胎生的介紹與定義:


Shark eggs are fertilized internally. The male has a pair of
claspers on its pelvic fins that transfer sperm into the reproductive
tract of the female.

Some species of sharks are oviparous;
they lay eggs that hatch outside the mother’s body.

These sharks release their eggs after encasing them in protective coats.

Other species are ovoviviparous;
they retain the fertilized eggs in the oviduct.
Nourished by the egg yolk,
the embryos develop into young that are born afterhatching within the uterus.

 A few species are viviparous;
the young develop within the uterus and obtain nourishment prior to birth
by receiving nutrients from the mother’s blood through a yolk sac placenta,
by absorbing a nutritious fluid produced by the uterus, or by eating other eggs.


也就是說,在目前的學界裡,魚類還是使用卵胎生在介紹的





同樣在兩類的介紹裡:

Fertilization is external in most amphibians; the male
grasps the female and spills his sperm over the eggs as the female
sheds them (see Figure 34.23c). Amphibians typically
lay their eggs in water or in moist environments on land; the
eggs lack a shell and dehydrate quickly in dry air. Some amphibian
species lay vast numbers of eggs in temporary pools,
and egg mortality is high. In contrast, other species lay relatively
few eggs and display various types of parental care. Depending
on the species, either males or females may house
eggs on their back (Figure 34.24), in their mouth, or even in
their stomach. Certain tropical tree frogs stir their egg masses
into moist, foamy nests that resist drying. There are also
some ovoviviparous and viviparous species that retain the
eggs in the female reproductive tract, where embryos can develop
without drying out.


說明了兩生類也是使用著卵胎生的說法。



















所以,根據這些資料的推論歸納
目前,我們該捨棄不用的,
是屬於爬蟲類的卵胎生,而不是將魚類及兩生類都做一併的刪除,

畢竟這是世界都有的知識語言,
不是為了說避免學生搞混而刪除一詞省去紛爭與麻煩,

念生物的老師都知道,生物是永遠念不完的,
因為會一直有新的知識出現,甚至推翻以往的觀念,

我們現在要學的東西,是將現有的知識傳達,
而不是眼不見為淨!






arrow
arrow
    全站熱搜

    米蘭 發表在 痞客邦 留言(0) 人氣()