Animal species have male and female specimens, and so do plants. Do plants and
animals have a common ancestor that already had specimens of male and female
gender? Does sexual terminology mean something completely different when applied
to plants as opposed to animals? TIA

Peace

Sex is a whole lot less rigidly male and female than you might think.
Many flowering plants have flowers with both male and female parts.
Others have separate male and female flowers on the same plant. Some
have male and female flowers on separate plants. Some have a mix of
bisexual and unisexual flowers on each plant. Among plant species that
have separate male and female specimens, it is not usually a case of X
and Y chromosomes as in mammals, though that does exist in some
species. Don't forget, too, that the sporophyte generation of a
moss, fern, liverwort, or flowering plant has no gender at all. Also
many species eschew sex almost completely, reproducing entirely
vegetatively or clonally.

Many animal species are funny sexwise as well--change sex during
lifetime (certain fish) , reproduce without males (aphids), have
gender determined by incubation temperature (crocodilians), are
hermaphrodites (slugs and worms), or reproduce asexually (flatrworms,
etc.)

Don't even get started on fungi, where there's no male and female per
se, just different complementary strains of the same species.
Microbes and algae...well, they do all sorts of different things, some
of which are just plain weird. And what about that little goober they
found living on lobster lips--it reproduces by dissolving its own guts
and rearranging them as young, splitting open and dying to release
them. I tell you, SF writers have not yet come up with much that
nature hasn't thought of.

I suspect it's not so much male and female that nature is after, but a
continuous mixup of genetic material. Asexually reproducing entities
can skip even that.

M. Reed
Texas A&M



Elaine Jackson wrote:

Animal species have male and female specimens, and so do plants. Do plants and
animals have a common ancestor that already had specimens of male and female
gender? Does sexual terminology mean something completely different when applied
to plants as opposed to animals? TIA

Peace

--
ÿWPC5

Thank you for your help. Actually I was already familiar with a few of the
examples you cite. (One or two I'd been aware of for some time, and naturally I
tried to answer this question with my own resources first.) But here's what I'm
wondering: I know that certain things like eyes and wings have evolved
independently in different species. Did sex evolve independently in plants and
animals? And if it did, in what sense is it the same thing in those two cases?
(Incidental question: What characteristics have plants and animals inherited
from their common ancestors?)

Peace


"Monique Reed" wrote in message
...
| Sex is a whole lot less rigidly male and female than you might think.
| Many flowering plants have flowers with both male and female parts.
| Others have separate male and female flowers on the same plant. Some
| have male and female flowers on separate plants. Some have a mix of
| bisexual and unisexual flowers on each plant. Among plant species that
| have separate male and female specimens, it is not usually a case of X
| and Y chromosomes as in mammals, though that does exist in some
| species. Don't forget, too, that the sporophyte generation of a
| moss, fern, liverwort, or flowering plant has no gender at all. Also
| many species eschew sex almost completely, reproducing entirely
| vegetatively or clonally.
|
| Many animal species are funny sexwise as well--change sex during
| lifetime (certain fish) , reproduce without males (aphids), have
| gender determined by incubation temperature (crocodilians), are
| hermaphrodites (slugs and worms), or reproduce asexually (flatrworms,
| etc.)
|
| Don't even get started on fungi, where there's no male and female per
| se, just different complementary strains of the same species.
| Microbes and algae...well, they do all sorts of different things, some
| of which are just plain weird. And what about that little goober they
| found living on lobster lips--it reproduces by dissolving its own guts
| and rearranging them as young, splitting open and dying to release
| them. I tell you, SF writers have not yet come up with much that
| nature hasn't thought of.
|
| I suspect it's not so much male and female that nature is after, but a
| continuous mixup of genetic material. Asexually reproducing entities
| can skip even that.
|
| M. Reed
| Texas A&M
|
|
|
| Elaine Jackson wrote:
|
| Animal species have male and female specimens, and so do plants. Do plants
and
| animals have a common ancestor that already had specimens of male and female
| gender? Does sexual terminology mean something completely different when
applied
| to plants as opposed to animals? TIA
|
| Peace
|
| --
| ÿWPC5

This answer gets rather technical. To simplify the answer, only
flowering plants will be considered. Flowering plants are the majority
of living plant species.

Technically, what most people call individual plants are sexless
sporophytes. Plants have an alternation of generations with a
sporophyte alternating with a gametophyte in the life cycle. Phyte
means plant. Gametophytes produce the sperm and eggs, which are
gametes. Sporophytes are sexless and produce spores. The sporophytes
are the dominant organisms that most people call plants. The male
gametophytes are pollen grains produced in the stamens. The female
gametophyte consists of a usually eight-celled embryo sac in the
carpel or pistil of the flower. The gametophytes are dependent on the
sporophyte.

Most plant species can produce both male and female gametophytes on
the same sporophyte. Only about 4% of flowering plant species produce
separate "male" and "female" sporophytes. The quotes around male and
female are used because the sporophyte is technically sexless but
occasionally produces only staminate or only carpellate flowers. These
are termed dioecious species. Examples include holly, asparagus,
persimmon, pussy willow, kiwi, pistachio, hops, bittersweet, date palm
and fig. Note that an individual plant is not dioecious, just the
species is dioecious. An individual plant of a dioecious species is
either "male" or "female." The preferred term for a "male" sporophyte
is a staminate plant. The preferred term for a "female" sporophyte is
a carpellate plant or pistillate plant.

Animals and plants do not have a recent common ancestor. Their common
ancestor would probably have been a single-celled organism.

There are some major differences between plant and animal sexual
reproduction but also a lot of similarities. In plants, gametophytes
have sex organs and sporophytes do not. Pollen grains contain sperm,
which functions like animal sperm. A plant sperm fertilizes the egg in
the embryo sac of the flower. Terms such as fertilization, zygote and
embryo are applied to both plants and animals and have the same
meaning in both. Plant pollination is roughly equivalent to copulation
or sexual intercourse in animals. Some animal sex terms do not apply
to plants such as fetus.


David R. Hershey


"Elaine Jackson" wrote in message news:5Fj9d.658765$gE.514467@pd7tw3no...
Animal species have male and female specimens, and so do plants. Do plants and
animals have a common ancestor that already had specimens of male and female
gender? Does sexual terminology mean something completely different when applied
to plants as opposed to animals? TIA

Peace

Animal species have male and female specimens, and so do plants.

Not strictly true. Some animals, like snails & aphids, are hermaphroditic some
of the time.
On the other hand, most of the flowering plants have male & female elements in
the same flower or on the same plant.

Do plants and animals have a common ancestor that already had specimens of
male and female gender?

Probably not. The male & female elements were carried on the same organism, but
I will leave the experts to answer that one.

Does sexual terminology mean something completely different when applied to
plants as opposed to animals?

Not really. In animals, the female produces eggs, ova. The male produces sperm
cells which are carried to the eggs, either externally in the lower animals or
internally in the higher animals.
In flowering plants, the female part of the flower contains an ovary, which
contains little eggs, called ovules. The male part of the flower, or if
separate, the male flowers, called staminate, produce pollen, which essentially
contains sperm cells. Through pollination, the pollen cells manage to get to
the ovules through many different mechanisms, sometimes wind, sometimes
insects, sometimes self-pollination, etc. The terminology & mechanics are
different in plants, but the basic process is the same.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)

In article c4p9d.660794$gE.331977@pd7tw3no,
Elaine Jackson wrote:
Thank you for your help. Actually I was already familiar with a few of the
examples you cite. (One or two I'd been aware of for some time, and
naturally I
tried to answer this question with my own resources first.) But here's what
I'm
wondering: I know that certain things like eyes and wings have evolved
independently in different species. Did sex evolve independently in plants and
animals? And if it did, in what sense is it the same thing in those two cases?

It depends on how you define sex. If you mean exchange of genetic
material between individuals, it goes back to the bacteria.

If you mean heterogameity, i.e. the condition in which there are two
kinds of gametes, large ones that are mostly sessile and contain
nutrition for the embryo and small motile ones that consist mostly of a
nucleus and a means of propulsion, I don't know how many times it was
invented independently. It almost certainly wasn't present in any
common ancestor of animals and plants, because AFAIK, it doesn't occur
in single celled organisms.

If you mean separate male and female organisms, this condition has
developed innumerable times independently in animals. As has been
explained by others, plants have a system called alternation of
generations, so even dioecious species don't really have male and
female individuals in the animal sense.

If you mean genetic sex determination, AFAIK, very little is known
about this is in invertebrates. In vertebrates, it's standard in
mammals, birds and frogs (dunno about other amphibians). It occurs in
some fish and some reptiles, but even within a taxon as small as a
family some species may have GSD, some may have environmental sex
determination, and some may have a combination. It's not necessarily
implemented with different chromosomes, either. It may be controlled
by one or more individual genes. (It's actually like that in mammals,
but less visible -- there's a single gene called TDF - testis
determining factor -- which is normally only on the Y chromosome, but
it can get translocated to the X, producing XX males.) In mammals,
frogs, and some fish males are heterochromatic (XY) while females are
homochromatic (XX). The reverse is true in birds. So this trait too
has arisen numerous times even in just the vertebrates.

Note that some seed plants (and fungi) have mating types, of which
there are usually more than two. Plants of the same mating type are
infertile with each other. Sweet cherries are a well known example --
they have at least eight mating types. I suppose these mating types
could be regarded as sexes in a very restricted sense, and this could
be overgeneralized to any plant that isn't self-fertile.

(Incidental question: What characteristics have plants and animals
inherited from their common ancestors?)

How to be a eucaryotic cell. This takes up a substantial part of the
genome, and is the reason behind the tag line that we share half our
genes with the banana, which is more apparent in some individuals than
in others! ;-)

This is good stuff. I'd like to ask a couple follow-up questions if I may:

Is it correct to say that, in any scheme in which there are exactly two kinds of
gametes, one of them makes the journey to the other, and the latter nourishes
the embryo?

Are two-gender systems more prevalent? (It seems plausible they would be most
efficient, 2 being the smallest integer bigger than 1.)

If the idea of mating types is overgeneralized in the way you indicate, what
absurdity results?

Can you recommend any good references for finding out more about this kind of
thing?

Thanks again for your help.

Peace

wrote in message
.. .
| In article c4p9d.660794$gE.331977@pd7tw3no,
| Elaine Jackson wrote:
| Thank you for your help. Actually I was already familiar with a few of the
| examples you cite. (One or two I'd been aware of for some time, and
| naturally I
| tried to answer this question with my own resources first.) But here's what
| I'm
| wondering: I know that certain things like eyes and wings have evolved
| independently in different species. Did sex evolve independently in plants
and
| animals? And if it did, in what sense is it the same thing in those two
cases?
|
| It depends on how you define sex. If you mean exchange of genetic
| material between individuals, it goes back to the bacteria.
|
| If you mean heterogameity, i.e. the condition in which there are two
| kinds of gametes, large ones that are mostly sessile and contain
| nutrition for the embryo and small motile ones that consist mostly of a
| nucleus and a means of propulsion, I don't know how many times it was
| invented independently. It almost certainly wasn't present in any
| common ancestor of animals and plants, because AFAIK, it doesn't occur
| in single celled organisms.
|
| If you mean separate male and female organisms, this condition has
| developed innumerable times independently in animals. As has been
| explained by others, plants have a system called alternation of
| generations, so even dioecious species don't really have male and
| female individuals in the animal sense.
|
| If you mean genetic sex determination, AFAIK, very little is known
| about this is in invertebrates. In vertebrates, it's standard in
| mammals, birds and frogs (dunno about other amphibians). It occurs in
| some fish and some reptiles, but even within a taxon as small as a
| family some species may have GSD, some may have environmental sex
| determination, and some may have a combination. It's not necessarily
| implemented with different chromosomes, either. It may be controlled
| by one or more individual genes. (It's actually like that in mammals,
| but less visible -- there's a single gene called TDF - testis
| determining factor -- which is normally only on the Y chromosome, but
| it can get translocated to the X, producing XX males.) In mammals,
| frogs, and some fish males are heterochromatic (XY) while females are
| homochromatic (XX). The reverse is true in birds. So this trait too
| has arisen numerous times even in just the vertebrates.
|
| Note that some seed plants (and fungi) have mating types, of which
| there are usually more than two. Plants of the same mating type are
| infertile with each other. Sweet cherries are a well known example --
| they have at least eight mating types. I suppose these mating types
| could be regarded as sexes in a very restricted sense, and this could
| be overgeneralized to any plant that isn't self-fertile.
|
| (Incidental question: What characteristics have plants and animals
| inherited from their common ancestors?)
|
| How to be a eucaryotic cell. This takes up a substantial part of the
| genome, and is the reason behind the tag line that we share half our
| genes with the banana, which is more apparent in some individuals than
| in others! ;-)

"Elaine Jackson" wrote in
news:nhC9d.29785$a41.4982@pd7tw2no:

This is good stuff. I'd like to ask a couple follow-up questions
if I may:

Is it correct to say that, in any scheme in which there are
exactly two kinds of gametes, one of them makes the journey to the
other, and the latter nourishes the embryo?


Not really, even in humans, the egg has its own journey to make. It
is much shorter than the distance that the sperm needs to go, but
fertilization occurs somewhere in the faloppian tubes, and not on
the surface of the ovary. Many molluscs and other oceanic animals
release the ova and sperm into the water, and neither parent
nourishes the resulting zygote. The fusion of the two cells becomes
the embryo, you could say that one has more stored resources than
the other, but that can go away rapidly when the embryo starts to
hunt and eat.

Are two-gender systems more prevalent? (It seems plausible they
would be most efficient, 2 being the smallest integer bigger than
1.)

This planet seems to only have either one or two genders. There are
some fungi that don't really have morphological distinctions between
the genders, and there are more than two "types", but you really
only need two different "types" to get successful "mating". I have
heard of no organism that requires genetic input from a third or
fourth party in order for reproduction to occur.


If the idea of mating types is overgeneralized in the way you
indicate, what absurdity results?

People might start calling something "male" just because it produces
a microgamete, and "female" because it produces a macrogamete, then
assign roles to the different sexes.


Can you recommend any good references for finding out more about
this kind of thing?

Thanks again for your help.


Sean

In article nhC9d.29785$a41.4982@pd7tw2no,
Elaine Jackson wrote:
This is good stuff. I'd like to ask a couple follow-up questions if I may:

Is it correct to say that, in any scheme in which there are exactly two
kinds of
gametes, one of them makes the journey to the other, and the latter nourishes
the embryo?

No. Someone mentioned the many marine animals in which sperm and ova
are both released into moving water. In that case, sperm and ova can
at least be distinguished as such -- the ova are larger and contain
yolk, while the sperm are smaller, motile and more numerous. There are
organisms in which the gametes are identical, including the true slime
molds (myxomycetes). These creatures have a large (up to a meter in
diameter in rare cases) mobile diploid stage, which sporulates. Each
spore germinates into an amoeba-like haploid stage which can grow a
flagellum in a wetter environment. These haploid forms can multiply by
fission for many generations, but when two of different mating type
meet, they fuse, and produce a diploid plasmodium which can grow to
respectable size. The species we were working with had many mating
types -- we found about a dozen from a pretty small sample of
individuals. Myxomycetes were regarded as fungi at the time, but now
they've been relegated to the grab bag of protista of uncertain
affinity, a great place to look for critters with bizarre reproductive
biology.

Are two-gender systems more prevalent? (It seems plausible they would be most
efficient, 2 being the smallest integer bigger than 1.)

It's plausible because DNA contains two strands, and because diploid
organisms have two sets of chromosomes, one from each parent, and
gametes are haploid (one set of chromosomes). In seed plants, the
haploid generation has been reduced to a few cells. In lower plants,
like mosses and ferns, the haploid generation is visible and
independent, but still secondary. In true slime molds, the two
generations are more or less equal in "importance". There are a lot of
critters, fungi, protista (IIRC including some algae), in which the
haploid is the main form and the diploid forms briefly and sporulates.
In many but not all of these critters, there are not only no genders,
but no heterogameity -- no sperm or eggs. All gametes are the same.

If the idea of mating types is overgeneralized in the way you indicate, what
absurdity results?

It would mean that every individual was a unique mating type, which is
indistinguishable from the common situation in which plants are not
self-fertile, which different species enforce by a wide variety
of methods.

Can you recommend any good references for finding out more about this kind of
thing?

Leaf through some college level intro biology texts to find some that
have an approach you like, to get a grasp of basic biology. Read some
of Steven Jay Gould's books of essays on biology and evolution. I
remember some essays described some very strange life cycles.
Scientific American publishes books with collections of articles on a
single topic. Perhaps there's one which will interest you. Most
universities allow members of the general public to use their
libraries, although you may have to pay a fee to be allowed to borrow
books. The Tree of Life project is a good place to find out about the
affinities of different groups of organisms, and each page has
references to the literature. http://tolweb.org

Several universities have free online self-study biology courses, and
many have the materials for conventional courses on the web.

A couple of things to remember when you study biology: One, nothing
makes sense without eveolution by natural selection. It's as
fundamental to biology as atomic theory is to chemistry. Two, the real
world is a very complex, messy place, and life on earth has had at
least 3.5 billion years to develop and adapt to the complexity, so just
about every generalization you can make will have exceptions. I
suppose I can add Three: humans, mammals and even vertebrates are
large, visible critters, but they are only a very small fraction of
species and the way they do things is not the standard for everything
else, even though far more is known about them than about any other
taxa. So try not to be anthropocentric, mammal-centric or even
vertebrate-centric!

I hope some other members of this group will make better and more
specific reading suggestions than I have.

You've been very informative. I appreciate it. Thanks.