[ndigila]

Correct me if I'm wrong anywhere.

According to evolution, the earliest forms of life reproduced asexually. In the modern day world, majority of the world's dominant creatures reproduced sexually.

I'm concerned about the transition from asexual to sexual reproduction.

If at one point you had only asexual creatures, living in the same environment, eating the same food, having the same enemies, etc, etc, What would cause these asexuals to evolve having female reproductive organs, and others having male reproductive organs? How did the distinction between male and female evolve? What about the "information" on how to have sex, where did it come about and how does it play in this evolutionary process?

Is it possible that species could have become extinct even before it started? i.e. having a species in which only males or females evolved and they became extinct due to inability to reproduce?

Is it possible that a species could have evolved more than once? Say, hypothetically, that when human beings evolved, only males evolved. Is it possible for the species to evolve again?

I'm not trying to argue, just asking honest questions because I'm somewhat ignorant about this issue

[Wamax74.]

The first man was asexual (Adam). God felt he was lonely and he created the complement (Eve).

[grip_daddy]

What I know is that evolutionary, transition is much more possible from sexual to asexual, but not the other way round. Scientists think that in about the year 3000, only female species of the human race will be in existence.

[KAVOI]

Originally Posted by ndigila

Correct me if I'm wrong anywhere.

According to evolution, the earliest forms of life reproduced asexually. In the modern day world, majority of the world's dominant creatures reproduced sexually.

I'm concerned about the transition from asexual to sexual reproduction.

If at one point you had only asexual creatures, living in the same environment, eating the same food, having the same enemies, etc, etc, What would cause these asexuals to evolve having female reproductive organs, and others having male reproductive organs? How did the distinction between male and female evolve? What about the "information" on how to have sex, where did it come about and how does it play in this evolutionary process?

Is it possible that species could have become extinct even before it started? i.e. having a species in which only males or females evolved and they became extinct due to inability to reproduce?

Is it possible that a species could have evolved more than once? Say, hypothetically, that when human beings evolved, only males evolved. Is it possible for the species to evolve again?

I'm not trying to argue, just asking honest questions because I'm somewhat ignorant about this issue

Asexual reproduction is a form of reproduction which does not involve meiosis, ploidy reduction, or fertilization. Asexual reproduction only takes one parent. A more stringent definition is agamogenesis which refers to reproduction without the fusion of gametes. Asexual reproduction is the primary form of reproduction for single-celled organisms such the archaea, bacteria, and protists. Many plants and fungi reproduce asexually as well. While all prokaryotes reproduce asexually (without the formation and fusion of gametes), mechanisms for lateral gene transfer such as conjugation, transformation and transduction are sometimes likened to sexual reproduction.[1]

The lack of sexual reproduction is relatively rare among multicellular organisms, for reasons that are not completely understood. Current hypotheses suggest that, while asexual reproduction may have short term benefits when rapid population growth is important or in stable environments, sexual reproduction offers a net advantage by allowing more rapid generation of genetic diversity, allowing adaptation to changing environments.

Because asexual reproduction does not require the formation of gametes (often in separate individuals) and bringing them together for fertilization, it occurs much faster than sexual reproduction and requires less energy. Asexual lineages can increase their numbers rapidly because all members can reproduce viable offspring. In sexual populations with two genders, some of the individuals are male and cannot themselves produce offspring. This means that an asexual lineage will have roughly double the rate of population growth under ideal conditions when compared with a sexual population half composed of males. This is known as the two-fold cost of sex. Other advantages include the ability to reproduce without a partner in situations where the population density is low (such as for some desert lizards), reducing the chance of finding a mate, or during colonisation of isolated habitats such as oceanic islands, where a single (female) member of the species is enough to start a population.

Another consequence of asexual reproduction, which may have both benefits and costs, is that offspring are typically genetically similar to their parent, with as broad a range as that individual receives from one parent. The lack of genetic recombination results in fewer genetic alternatives than with sexual reproduction. Many forms of asexual reproduction, for example budding or fragmentation, produce an exact replica of the parent. This genetic similarity may be beneficial if the genotype is well-suited to a stable environment, but disadvantageous if the environment is changing. For example, if a new predator or pathogen appears and a genotype is particularly defenseless against it, an asexual lineage is more likely to be completely wiped out by it. In contrast, a lineage that reproduces sexually has a higher probability of having more members survive due to the genetic recombination that produces a novel genotype in each individual. Similar arguments apply to changes in the physical environment. From an evolutionary standpoint, one could thus argue that asexual reproduction is inferior because it stifles the potential for change. However, there is also a significantly reduced chance of mutation or other complications that can result from the mixing of genes. A 2004 article in the journal Nature reported that the modern arbuscular mycorrhizas fungi, which reproduces asexually, is identical to fossil records dating back to the Ordovician period, 460 million years ago.[
man has never experienced asexual reproduction.

[ndigila]

Originally Posted by KAVOI

Asexual reproduction is a form of reproduction which does not involve meiosis, ploidy reduction, or fertilization. Asexual reproduction only takes one parent. A more stringent definition is agamogenesis which refers to reproduction without the fusion of gametes. Asexual reproduction is the primary form of reproduction for single-celled organisms such the archaea, bacteria, and protists. Many plants and fungi reproduce asexually as well. While all prokaryotes reproduce asexually (without the formation and fusion of gametes), mechanisms for lateral gene transfer such as conjugation, transformation and transduction are sometimes likened to sexual reproduction.[1]

The lack of sexual reproduction is relatively rare among multicellular organisms, for reasons that are not completely understood. Current hypotheses suggest that, while asexual reproduction may have short term benefits when rapid population growth is important or in stable environments, sexual reproduction offers a net advantage by allowing more rapid generation of genetic diversity, allowing adaptation to changing environments.

Because asexual reproduction does not require the formation of gametes (often in separate individuals) and bringing them together for fertilization, it occurs much faster than sexual reproduction and requires less energy. Asexual lineages can increase their numbers rapidly because all members can reproduce viable offspring. In sexual populations with two genders, some of the individuals are male and cannot themselves produce offspring. This means that an asexual lineage will have roughly double the rate of population growth under ideal conditions when compared with a sexual population half composed of males. This is known as the two-fold cost of sex. Other advantages include the ability to reproduce without a partner in situations where the population density is low (such as for some desert lizards), reducing the chance of finding a mate, or during colonisation of isolated habitats such as oceanic islands, where a single (female) member of the species is enough to start a population.

Another consequence of asexual reproduction, which may have both benefits and costs, is that offspring are typically genetically similar to their parent, with as broad a range as that individual receives from one parent. The lack of genetic recombination results in fewer genetic alternatives than with sexual reproduction. Many forms of asexual reproduction, for example budding or fragmentation, produce an exact replica of the parent. This genetic similarity may be beneficial if the genotype is well-suited to a stable environment, but disadvantageous if the environment is changing. For example, if a new predator or pathogen appears and a genotype is particularly defenseless against it, an asexual lineage is more likely to be completely wiped out by it. In contrast, a lineage that reproduces sexually has a higher probability of having more members survive due to the genetic recombination that produces a novel genotype in each individual. Similar arguments apply to changes in the physical environment. From an evolutionary standpoint, one could thus argue that asexual reproduction is inferior because it stifles the potential for change. However, there is also a significantly reduced chance of mutation or other complications that can result from the mixing of genes. A 2004 article in the journal Nature reported that the modern arbuscular mycorrhizas fungi, which reproduces asexually, is identical to fossil records dating back to the Ordovician period, 460 million years ago.[
man has never experienced asexual reproduction.

Ok, you've not answered the questions. Your post simply explains the benefits of sexual over asexual and vice versa. What I'm really looking for is an explanation of the transition from asexual to sexual reproduction.

[Type R]

There are even some animals - fish, I think - that can swap sex organs. Imagine, being a babe this year, next year you're a guy!!!

There are others with both male and female organs and each animal self-fertilizes!!! Yikes!!!

ndigila, you should do a master's/PhD in 'self organizing systems.' - very interesting topic.

[Type R]

The proper title of this thread should have been "The Genesis of Sex."

[ndigila]

Originally Posted by Type R

ndigila, you should do a master's/PhD in 'self organizing systems.' - very interesting topic.

Man, I wish I could. If I was to study every topic I was interested in, I'd be in school the rest of my life.

[ndigila]

Originally Posted by Type R

The proper title of this thread should have been "The Genesis of Sex."

Maybe, but I'm more interested in its Genesis from an evolutionary perspective.

[Tripple Seven]

Sir, evolution is not a clear cut topic not to bring in my religious beliefs yet. I cannot really assert that most world species reproduced a sexually n that with time they are diminishing. As the other reader suggested there are lots of advantages of sexual over asexual. This could better place the sexual over the a sexual. Lack of genetic recombination in a sexual case leads to fewer genetic alternatives. Budding or fragmentation, produce an exact parent replica. This is quite disadvantageous to changing environment. In world pandemics, genetic recombination allow adaptation that u can easily summarize as a tool for survival for the fittest. There are quite a bunch of species that are heterogamy. Others turn to asexual or sexual depending on various reasons. And I don’t have a cause to xplain how female turkey can produce fertile eggs without a male. In ending, I don’t have any feasible reason to believe, with facts or otherwise, that at one time almost all species were asexual n that over time the trend is changing. Gud luck though.