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Carnivore OR Herbivory Which one came first?

  1. Apr 13, 2013 #1
    As Appears,

    Considering life originated from oceans,alge...fishes and so on and following evolution ,just wondering which one above developed first? carnivore OR herbivory?

    Thanks,
     
  2. jcsd
  3. Apr 13, 2013 #2

    Borek

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    Staff: Mentor

    Do the classification make much sense on early Earth, before photosynthesis?

    What if omnivores were first and then specialized? At which moment do you call something a herbivore/carnivore?

    IMHO question as asked is way too ambiguous for any meaningful answer.
     
  4. Apr 13, 2013 #3
    Are you talking only about the ingestion of large organisms?


    There are other heterotrophic lifestyles. I have reason to suspect that other lifestyle choices came before either.

    Animals in the Edicarian period, which came right before the Cambrian period, didn't do either. There are large fossils of animals in the Edicarian period, especially of an animal called the rangomorph. There are no bite marks on any of these Edicarian animals. Furthermore, there is no sign of any hard part that could bite among the animals of the Edicarian. None of them had jaws or even a mouth. They couldn't be either carnivores or herbivores.

    The first animals that could bite appear at the beginning of the Cambrian period. There is a fossil at the very end of the Edicarian period showing some mollusk scraping up food with his rasping "tongue". That is the only preCambrian animal that shows a mouth with hard parts.

    So far as paleontologists can determine, the first animals that exhibit either predation or herbivory appear in the Cambrian. Although there are traces of animals before that, none of the preCambrian animals have the means to chew up or absorb a macroscopic animal.

    Predatory and herbivory behavior appear almost simultaneously in the Cambrian. I am not sure that the animals in the early Cambrian are specialized for either. Hard parts developed on animals that could be used for either life-style. Specialization in either may not have arrived until much later.

    Some animals that lived in the Edicarian period didn't have any gut or opening for food. The rangomorphs were among the first animals. All the rangomporphs had were branching. Plants develop this configuration to catch sunlight. Animals don't need sunlight. However, branching could have been very useful for absorbing dissolved nutrients from the water.

    I don't know of a fossil of any specialized predator until the middle Cambrian. Some of the animals in the Burgess shale are clearly predators. Some may have scraped algae off rock.

    Cnidarians (jelly fish, coral) may have developed a predatory lifestyle first. However, many corals get their food both from animals they catch and from algae that grow in their guts. So maybe they would better be called omnivores. There may have been cnidarians around in the Edicarian. So maybe predation came first in cnidarians.

    Vertebrates seem to arrive in force at the end of the Ordivician. However, the first vertebrates didn't have jaws. They had gills that appear very much like nets. So it seems the first vertebrates filtered plankton. They don't develop jaws until the middle of the Silurian. I doubt there were any vertebrates which were committed carnivores or committed herbivores before then.

    Anyway, I have three candidates for the first animal lifestyle.

    1) Plankton filtering.
    -Plankton includes both small animals, small plants and microbes that are between the kingdoms. So I don't know if you would count this as either.
    -The first vertebrate gills seem adapted to straining plankton rather than for respiration. The first fish were jawless. They could not have been carnivores or herbivores.
    -Sponges catch microbes.


    2) Diffusion of dissolved nutrients into the cells.
    -The decay process dissolves many nutrients in water. Some creatures can simply assimilate those nutrients from the water. In a way, this is scavenging.
    -There is speculation that the animals that lived in the Edicarian era primarily lived by absorbing nutrients from the water.
    -Sponges also absorb nutrients direct from the water.

    3) Omnivory
    -The first animals with hard parts probably did not care what they ate.
    -Land animals have to specialize because land plants have cellulose which is hard to digest. However, marine animals don't always have to make such a hard choice. Many algae are as easy to digest as meat because they don't have cellulose.


    I conjecture that the first animals probably absorbed nutrients by diffusion until the Cambrian. Then, animals with hard parts started to collect plankton. After that, a few animals became omnivores. Then, predation and herbivory developed simultaneously in parallel from omnivory.
     
  5. Apr 13, 2013 #4
    Thanks Darwin123

    Sorry if the question wasn’t rich enough.
    Just a tiresome to comprehend what happened to living creatures to become carnivore. Apparently the main point could be changing in autotrophs to heterotrophy skill, which is a changes in carbon processing ability!?Ish!
    Not only changes in food chain but rather than that a physical/chemical change? (And where Carnivorous plant stands is yet there)

    @Borek: Sorry I am not specifically a paleontologist and have a “simplicity syndrome” but definitely not before photosynthesis!! :)


    Cheers,
     
  6. Apr 14, 2013 #5
    I was just suggesting that you are looking at the problem to narrowly. There are a lot of lifetstyles which are not carnivorous or herbivorous. It is very likely that the first feeding methods did not involve either. Let me give you a list of alternatives.


    When discussing the origins of either food or sex, we have to start with microbes. Biochemistry has been evolving about 4 BY. Organisms that are truly multicellular have been evolving only 1 BY. Therefore, the evolution of our molecules has been mostly dominated by one celled organisms.

    I think the earliest living cells on earth probably were heterotrophs that fed by osmosis. These cells, which originated about 4 BYA, were probably were a lot like some modern bacteria. The food originally used was very likely non-biological, originating in whatever organic molecules were around. Note that food does not have to be complex or even alive. Hence, osmotrophy doesn’t really distinguish between carnivory and herbivory.

    http://en.wikipedia.org/wiki/Osmotrophy
    “Osmotrophy is the uptake of dissolved organic compounds by osmosis for nutrition. Organisms that use osmotrophy are osmotrophs. Some mixotrophic microorganisms use osmotrophy to derive energy.”

    Note autotrophs probably used osmotrophy, too. You can be a plant or an animal. Osmosis is not complicated.

    Eukarotes evolved maybe two billion years ago. One way of feeding eukaryotes have that is not available to bacteria is phagocytosis. Hence, much of our biochemistry probably evolved from phagocytosis.

    http://en.wikipedia.org/wiki/Phagocytosis
    “In cell biology, phagocytosis is the process of engulfing a solid particle by a phagocyte or a protist to form an internal phagosome (from Ancient Greek φαγεῖν (phagein) , meaning "to devour", κύτος, (kytos) , meaning "cell", and -osis, meaning "process"). Phagocytosis was revealed by Ilya Mechnikov in 1882. Phagocytosis is a specific form of endocytosis involving the vesicular internalization of solids such as bacteria, and is, therefore, distinct from other forms of endocytosis such as the vesicular internalization of various liquids.”

    The earliest animals, which originated “only” 800 MYA, probably fed by osmotrophy also. This is a good example of convergent evolution, because I am sure osmotrophs evolved far before multitrophy. Here is a link that suggests exactly that.

    http://www.astrobio.net/pressrelease/3224/eating-by-osmosis
    “Summary: New research shows that the oldest complex lifeforms on Earth likely fed by osmosis. The organisms lived in the oceans more than 540 million years ago and absorbed nutrients through their outer membrane. The study provides new insight into the evolution of life on Earth.
    The researchers studied two groups of modular Ediacara organisms, the fern-shaped rangeomorphs and the air mattress-shaped erniettomorphs. These macroscopic organisms, typically several inches in size, absorbed nutrients through their outer membrane, much like modern microscopic bacteria, according to the cover story of the Aug. 25, 2009 issue of the Proceedings of the National Academy of Sciences (PNAS), "Osmotrophy in modular Edicara organisms," by Marc Laflamme, Shuhai Xiao, and Michal Kowalewski.”


    Bring out your dead!

    Osmotrophy probably evolved into saprophy. The microorganisms simply grows in an area with a lot of dead organisms.

    http://en.wikipedia.org/wiki/Saprophytes
    “Saprophytes may refer to
    Saprotroph, a term used for organisms which obtain nutrients from dead organic matter (this term commonly applies to fungi)
    Saprophytes are a plant, fungus, or micro-organism, more accurately called myco-heterotrophs because they actually parasitize fungi, rather than dead organic matter directly. They live on dead or decomposing matter.”


    Then of course there are the scavengers.

    http://en.wikipedia.org/wiki/Scavenger
    “Scavenging is both a carnivorous and herbivorous feeding behavior in which the scavenger feeds on dead and decaying organic matter present in its habitat. [1] The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by consuming the dead animal and plant material. Decomposers and detritivores complete this process, by consuming the remains left by scavengers.”

    Inhale your food! Lets try filter feeding.
    http://en.wikipedia.org/wiki/Filter_feeder
    “Filter feeders (a sub-group of suspension feeders) are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish (including some sharks). Some birds, such as flamingos, are also filter feeders. Filter feeders can play an important role in clarifying water.”

    Specialization into carnivory or omnivory probably happened many times in earths history. Many types of animals and plants jumped back and forth between the two. Furthermore, animals seldom specialize completely into one or the other.

    Most animals are at least a little omnivorous. They may have preferences, but can supplement their diet with the other type of food. It is not true that an animal has to choose either one or the other. Specialization helps when the environment remains unchanging for a long time. However, in times of crisis it is best to eat anything.

    I suggest that you ask about which animals have switched from one to the other, and why. You would be surprised how many animals seem to have done that in earth history. There was never a single time when carnivory became omnivory, or omnivory became carnivory.

    Furthermore, they are not the only lifestyles.
     
  7. Apr 14, 2013 #6
    Sorry for being difficult. I will give some examples that occurred after the Cambrian explosion.

    There was no one time that herbivory or carnivory dominated. Most animal lineages flipped from one to another. Some many times. Some recently, some very long ago.

    Dinosaurs flipped back and forth. The following link describes some of the changes seen in dinosaur lineages. Note that there was no one transition point. It occurs again and again.

    http://www.academia.edu/737399/The_roles_of_herbivory_and_omnivory_in_early_dinosaur_evolution
    “The roles of herbivory and omnivory in earlydinosaur evolution”

    Mammals flipped back and forth, too. These links concern changes seen in mammal lineages. Again note that there is no one transition point. It occurs again and again.

    ttp://www.sciencedaily.com/releases/2012/04/120416154417.htm
    “They found that while some groups of mammals maintained steady diets, others changed their feeding strategies over time. Today's omnivores in particular -- a group that includes primates, bears, dogs and foxes -- came from ancestors that primarily ate plants, or animals, but not both, said co-author Samantha Price of the University of California Davis. While omnivorous mammals weren't always that way, plant-eaters and meat-eaters have diversified within a more well-worn path. Radical shifts were unlikely for these animals. Mammals that eat meat for a living, for example, never gave up their taste for flesh without transitioning through an omnivorous stage first. "Direct transitions from carnivory to herbivory were essentially nonexistent," said co-author Louise Roth of Duke University. "It's an intuitive result because it takes very different kinds of equipment to have those kinds of diets," she added.”


    http://www.pnas.org/content/early/2012/04/10/1117133109.full.pdf
    “Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history.

    We show that net diversification rate (the cumulative effect of speciation and extinction), differs signiicantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are in-
    termediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and sub-divide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores.”
     
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