Darwin and Evolution

[Thunderbird]

What do you mean by advanced? You have previously, if I recall, fallen into the trap of thinking reptiles are more advanced than fish, mammals more advanced than reptiles. Just how do you define advanced?

Off the top of my head, reptiles have a more advanced heart, skeletal structure, than fish.

 

Mammals can regulate body temp, bigger brains than reptiles. These are advancments.

[freeztar]

Off the top of my head, reptiles have a more advanced heart, skeletal structure, than fish.

 

How so?

Mammals can regulate body temp, bigger brains than reptiles. These are advancments.

 

They're adaptations suited for mammals.

 

The word "advancement" implies "better than".

Regulating body temp and bigger brains requires more energy, which can most certainly become a hinderance.

[Thunderbird]

How so?

 

 

They're adaptations suited for mammals.

 

The word "advancement" implies "better than".

Regulating body temp and bigger brains requires more energy, which can most certainly become a hinderance.

 

 

By advanced I mean.... well advanced.

 

What is a reptile?

The reptiles

The difference between amphibians and reptiles is that reptiles exhibit a suite of characteristics understandable as adaptations to life on land at increasing distance from water. Although many species of amphibians live on land in "/topic/adult", most have an aquatic "/topic/larval-stage-computer-jargon", and few can exist for long without moisture even during their terrestrial stages of life. Amphibians are tied to water—most species are not found more than a few meters from water or from moist soil, humus, or vegetation. Reptiles of many species are relatively liberated from water and can inhabit both "/topic/mesic" (moist) and "/topic/xeric" (dry) environments. Reptiles need water for various physiological processes, as do all living things, but some reptiles can obtain the water they need from the foods they eat and through conservative metabolic processes without drinking or by drinking only infrequently. Understanding the nature of reptiles requires focus on their techniques for maintaining favorable water balance in habitats where water may not be readily available and where moist microniches may be uncommon.

Characteristics

Most reptiles have horny skin, almost always cornified as scales or larger structures called scutes or plates. Such integuments resist "/topic/osmotic-3" movement of water from body compartments or tissues into the surrounding air or soil, thus minimizing "/topic/desiccate". There are times in the lives of snakes and lizards when their skin becomes "/topic/permeable" to water, as when the animals are preparing to shed their old skin. During such times they seek out favorable hiding places that protect them not only from predators but also from water loss. The combination of integumentary "/topic/impermeable" (most of the time) and innate preferences for favorable microclimates during vulnerable periods allows reptiles to retain body water rather than to lose it to arid surroundings. Some reptiles are known to drink water that condenses on their scales when they reside in cool burrows.

Added to the mechanisms for retaining body water is an "/topic/excretory-system" that is considerably advanced over those in fishes and many amphibians. The kidneys are integral components of the circulatory system. They allow constant, efficient "/topic/filtration-mathematics" of blood. Most aquatic organisms excrete nitrogenous waste as ammonia. Ammonia readily diffuses across skin or gills, provided plenty of water is present, but is not efficiently excreted by the kidneys. Ammonia is highly toxic, and animals cannot survive if this substance accumulates in their bodies. Terrestrial organisms excrete nitrogenous waste in the form of urea or "/topic/uric", which are less toxic and which require less water than does excretion of ammonia. Urea is the main nitrogenous waste in terrestrial amphibians, whereas uric acid (which requires very little water) is the main nitrogenous "/topic/effluent" in reptiles. Finally, some desert-dwelling reptiles have a remarkable ability to tolerate high plasma urea concentrations during drought. This characteristic allows the animals to minimize water loss that would be coincident with excretion. Rather than being excreted, nitrogenous waste is simply retained as urea, and water is conserved. When a rainfall finally occurs, reptiles (e.g., the desert tortoise Gopherus agassizii) drink copiously, eliminate wastes stored in the bladder, and begin filtering urea from the plasma. Within days their systems return to normal, and the tortoises store a large volume of freshwater in their bladders to deal with the next drought.

Feeding

 

 

 

Diversity of reptiles

Reptiles range in body form from crocodilians to squamates, tuatara, and turtles. This diversity borders on trivial, however, in comparison with the range of forms and lifestyles that existed during the "/topic/jurassic" and Cretaceous periods. This point can be further appreciated by considering locomotion among lizards with well-developed legs. Although some species are capable of quick movement, the gait of all lizards is basically the same as that of salamanders. The legs extend from the sides and must support the body through right angles, greatly limiting body mass and speed. Within the context of these constraints, lizards do quite well, but their locomotion remains relatively primitive. Truly advanced locomotion, with the legs directly under the body, occurs among mammals, but this pattern of limb suspension evolved in dinosaurs and was clearly a part of their long period of success. All extant reptiles are ectotherms, deriving their body heat from radiation, conduction, or "/topic/convection", whereas mammals and birds are endotherms, producing body heat by energy-consuming metabolic activity. Thus we see the primitive condition in the reptiles and the advanced condition in the birds and mammals. There is now good reason to believe that at least some dinosaurs were endotherms. Accordingly, it is important to keep in mind that the diversity of extant reptiles is but a fraction of the diversity exhibited by this class of vertebrates during earlier phases of its natural history.

 

Brain

The brain and spinal cord exhibit several advanced characteristics in reptiles relative to amphibians, including larger size and greater definition of structural divisions and greater development of the "/topic/cerebral". Neural connections between the "/topic/olfactory" bulbs, the "/topic/corpus-striatum", and several other "/topic/subcortical-in-medicine" structures have become clearly established in reptiles, and these connections have been conserved in subsequent evolution such that they are present in mammals, including humans. This set of connections is sometimes referred to as the "reptilian brain" or ""/topic/reptilian-complex"" and is thought to represent a "/topic/neural-circuit" necessary for the mediation of basic functions such as predation and mating as well as the affective concomitants associated with social behaviors ranging from cooperation to aggression. In the study of mammals, we speak of the regulation of emotion by components of the reptilian brain. Herpetologists are generally reluctant to speak of emotion in their animals, but they have no difficulty recognizing the existence of the neural circuit in question and in understanding that it contributes to social and reproductive activities. Whether this contribution is limited to the organization of motor patterns or whether emotion also is involved remains an open question.

 

 

What Is a Reptile?: Information and Much More from Answers.com

[Thunderbird]

And advanced can mean more complex. :)

 

 

Additionally, reptiles relied on giving birth to eggs. Eggs are basically left to hatch and fend for themselves. The new mammals evolved a system of reproduction which leaves the young to develop more fully inside the mother. After birth, the young are afforded extended parental care by the the reliable provision of the mother's mammary glands. Thus, the young can spend its energy in further physiological growth, rather than having to be immediately able to hunt and defend itself. Both these advances allowed more time for the development of a more complex organism and the cerebral system in the mammalian ancestry

 

THE* EVOLUTION OF MAMMALS

[Thunderbird]

Advanced, Complex, these are good words when discussing evolution. You guy's reaction to these words borders on onomatophobia.

[freeztar]

Advanced, Complex, these are good words when discussing evolution. You guy's reaction to these words borders on onomatophobia.

 

The reaction to such words is based on prior semantic confusions and a desire to make sure we are on the same page. Since it seems you are not implying "better", then I have no problem with your use of the word "advanced".

[Thunderbird]

The reaction to such words is based on prior semantic confusions and a desire to make sure we are on the same page. Since it seems you are not implying "better", then I have no problem with your use of the word "advanced".

 

I don't believe I've implied "better" on any post referring to animals, but I'd rather be an eagle than a salamander.:)

[CraigD]

I don't believe I've implied "better" on any post referring to animals, but I'd rather be an eagle than a salamander.:)

I, too, would “rather be a sparrow than a snail” :) but think of all the genetic complexity you’re sacrificing with that decision! ;)

 

Birds has genomes between 0.97 and 2.16, mean of 1.45 picograms. Salemanders, on the other hand, are the genetic heavyweights of the amphibian class, with genomes from 10.12 to 120.60, mean of 36.17 pg. We humans, as already mentioned, weigh in at 3.50 pg – genetically, we’ve got twice what the average bird has, but only a tenth of the average salamander.

 

As in post #22, all the nifty data is from Animal Genome Size Database, Release 2.0.

 

You gotta love cells and DNA. :) Once you’ve figured out they exists (which took millennia), in no time at all (less than a decade) you can weigh them, and within a generation, completely sequence them. Charles Darwin would have loved living now, I think.

[Thunderbird]

# of genes

Rice- 37,544

 

Humans-20,500

 

Do you know why my rice crispies contains more genitic info than I do.:)

[freeztar]

# of genes

Rice- 37,544

 

Humans-20,500

 

Do you no why my rice crispies contains more genitic info than I do.:)

 

Because they're more advanced than you.

(just a joke) :)

[Thunderbird]

Because they're more advanced than you.

(just a joke) :)

 

 

They taste better, :)

 

 

I would like to narrow the field of possible answers, if I may, it is not about our immune system, and not because of genetic engineering, it has to do with a main deference between plants and animals in general way.

[freeztar]

They taste better, :)

 

I'll take your word for it. :)

 

I would like to narrow the field of possible answers, if I may, it is not about our immune system, and not because of genetic engineering, it has to do with a main deference between plants and animals in general way.

 

:)

I'll give it some thought...

[CraigD]

# of genes

Rice- 37,544

 

Humans-20,500

Interesting figures, but weirdly precise.

 

Counting gene is much more difficult than finding the size of a genome (c-value, or equivalently, number of base pairs (c-value of 1 pg = 978,000,000 base pairs)) - You’ve got to find the genes initiators and terminators. So gene count are (with except for some very small, well understood genomes, such as yeast) always estimates.

 

20,500 sound a lot like a variation on the 2004 Human Genome Project announcement lowering the estimate for human protein-coding genes from 35,000 to 20,000-25,000. 37,544 seems impossibly precise – given the effort and attention given the human genome, I’d be surprised if more was known about the corn genome.

 

What’s your source, Thunderbird? :) I’m curious how they got such precise-looking numbers.

Do you know why my rice crispies contains more genitic info than I do.:lol:

LOL. Not to worry – rice may have a lot of genes, but once it’s been cooked - really cooked , crisped - you’d have to make some wild guesses to get any genetic info out of it. Cooking and DNA don’t go together well.

[Kayra]

Hmm.

While I can see the number of genes increasing in order to adapt to new or changing environments, would the gene count only decrease if there were an environmental stressor or energy requirement that promoted that?

 

What is the energy impact on the organism for carrying extra genetic material around?

 

Are all of the genes actually in use at any point in the life cycle?

 

Oops.. to much coffee today :)

[freeztar]

Hmm.

While I can see the number of genes increasing in order to adapt to new or changing environments, would the gene count only decrease if there were an environmental stressor or energy requirement that promoted that?

 

What is the energy impact on the organism for carrying extra genetic material around?

 

Are all of the genes actually in use at any point in the life cycle?

 

Oops.. to much coffee today :)

 

Good questions Kayra. I think you'll find this article a great read and it should answer some of your questions. :lol:

 

Annals of Science: Darwin’s Surprise: Reporting & Essays: The New Yorker

[Thunderbird]

Interesting figures, but weirdly precise.

 

Counting gene is much more difficult than finding the size of a genome (c-value, or equivalently, number of base pairs (c-value of 1 pg = 978,000,000 base pairs)) - You’ve got to find the genes initiators and terminators. So gene count are (with except for some very small, well understood genomes, such as yeast) always estimates.

 

20,500 sound a lot like a variation on the 2004 Human Genome Project announcement lowering the estimate for human protein-coding genes from 35,000 to 20,000-25,000. 37,544 seems impossibly precise – given the effort and attention given the human genome, I’d be surprised if more was known about the corn genome.

 

What’s your source, Thunderbird? :) I’m curious how they got such precise-looking numbers.LOL. Not to worry – rice may have a lot of genes, but once it’s been cooked - really cooked , crisped - you’d have to make some wild guesses to get any genetic info out of it. Cooking and DNA don’t go together well.

 

CragD, I will find the source on the rice and human DNA when I get back to work tomorrow.

 

Any guesses on why some plants have more genes than animals ?

[Eclogite]

Any guesses on why some plants have more genes than animals ?

Polyploidy?