Reproduction
From EvoWiki
Contents |
[edit] Introduction
Reproduction is the process by which one or more organisms make more organisms of the same species. It is one of the distinctive characteristics of life. The original organisms in the reproduction process are called the parents, and the newly formed organisms are called offspring.
During the process some or all of the DNA from the parent(s) is replicated and passed onto the offspring.
[edit] Types of reproduction
Reproduction may be broadly classified into one of two types. Asexual reproduction involves only a single parent, while sexual reproduction involves at least two parents.
[edit] Importance of reproduction
Reproduction is obviously important for its necessity in keeping life going. Since individual organisms tend to be mortal, life would quickly cease to be without some method of replication.
[edit] Evolution
More interestingly, reproduction plays a key role in evolution in several ways. It creates an avenue for mutation to take place and creates a population of organisms on which natural selection can operate.
Reproductive fitness is also one particular avenue of selection. Organisms that are well-suited to spreading their genes by having offspring have an advantage over organisms that do not, whether this refers to a fungus that produces more spores than its brethren, or a human that is able to attract a mate.
There are actually two major evolutionary reproductive strategies that act as attractors for most organisms, i.e. they tend to lean strongly toward one strategy or the other. These strategies are known as r-selection and K-selection. K-selected organisms tend to have few offspring, but invest energy heavily in each one to ensure it has a strong chance of spreading its genes further, while r-selected tend to invest very little in each offspring, but to produce them in large numbers to ensure that some will survive. Each strategy is adaptive in different niches.
[edit] Abiogenesis
The initiation of reproduction is thought by many to be the critical point at which abiogenesis could be said to have occurred. This is because once reproduction is happening Darwinian evolution can create new life forms from an original replicator. This is why many abiogenesis hypotheses posit that the first molecule of life was a nucleic acid, as these are the only molecules known to self-replicate.
[edit] Creationism
Failure to appreciate the significance of reproduction is characteristic of many common creationist arguments. This is especially true of arguments that claim that an increase in complexity is impossible without external guidance or design. The fact that organisms reproduce, and that natural selection will affect the kind of organism one finds over time shows the fundamental flaw in such arguments, as used against evolution.
