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Author Topic: Why are the offspring of some animals very small and others much larger?  (Read 7051 times)

Offline chris

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A very interesting question came out of the 5 Live phone-in this week. Why do some animals - like humans - have relatively large babies whilst other animals - like pandas - have relatively small babies? I'd be interested in your thoughts on this.

Chris


 

Offline RD

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... whilst other animals - like pandas - have relatively small babies?

Or Kangaroos ...


Quote
Newborn joey [baby kangaroo] sucking on a teat in the pouch ...
When the joey is born, it is about the size of a lima bean.
http://en.wikipedia.org/wiki/Kangaroo#Adaptations

If there is only sufficient nutrition (vegetation) for a few months of the year then there will be natural selection for a short gestation, and consequently smaller size at birth.
« Last Edit: 14/05/2009 08:01:26 by RD »
 

Offline Don_1

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Small babies mean short gestation periods, so the adult does not put too much energy into a process which may be futile if the young are born at a period of lean pickings. Harsh though it may be, a baby born at such times can be discarded without the adult having wasted too much energy, and can then quickly embark on a new pregnancy, which will hopefully result in a new baby being born during a more fruitful period.
 

Offline RD

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The large body size of the giant panda is an adaptation to the low nutritive quality of bamboo. Large animals with low body surface area to body volume have lower metabolic rates. The food requirements for sustaining metabolism therefore would be lower. This allows the panda survive on a poor nutrient diet. A larger body size would also obtain more resources.
http://www.geocities.com/rainforest/vines/2695/genetics.html

There is also the fact that herbivores are capable of becoming much larger than carnivores as they do not have to chase their dinner.
« Last Edit: 16/05/2009 09:16:20 by RD »
 

Offline davlin47

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Hello

A balance of the costs of producing an offspring, caring for an offspring, and the chance that it will survive in the environment. Cost to Benefit Ratio. For instance, some animals produce many offspring at once, which increases the probability that at least or two will survive. This increases the probability that the parental genes will be passed on to the next generation. On the other hand, offspring that are larger may need to compete for resources sooner. Humans aren't a good example. Think about whales. The calf has to be able to escape predators, even if the mother or the group provides some degree of protection. Simple, yet complex.

Thanks for sharing
« Last Edit: 28/10/2009 17:04:15 by BenV »
 

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