The Evolution of Structure and Function

Evolution provides the opportunity for organism to adapt to their environment (biotic and abiotic). Darwin’s phrase captured this idea in terms of “survival of the fittest.” How might the idea of co-evolution fit in with this concept of what drives evolution? (You’ll need to do some research on co-evolution on your own here).

Do structure and function evolve at the same time, or does one drive the other?

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If patterns and their related processes don’t have genes recording their changes over time, how are these patterns and processes in communites and ecosystems preserved and improved over millennia?

5 Responses to “The Evolution of Structure and Function”

  1. Tamar Bouchard says:

    Co-evolution seems to be a driving force in survival of the fittest, because predator and prey or parasite and host are dependent on each other for survive. What changes one is going to effect the change of the other. If one side of the interdependency does not adapt, then either the relationship is broken or the failing side will not survive. Adaptation ability seems to be very tied to fitness.

    Structure and function must evolve very closely, although only in the successful, fit, descendants. It would seem that a need for a functional change would come before the actual physical structural change, but mutations are mutations, they may or may not follow the perfect order of things. The “chicken and egg” conundrum is referred to in the lecture and it is a good corollary to the relationship of structure and function. Structural and functional changes are something like a test of which entities survive or are the salvation of descendants in need of survival support.

    Patterns and processes seem to be more about social behavior or interactions with other species in an environment that has been established. It would seem that genetics would not have to play a part in that. If something works and is effective, then it would make sense to do it that way, because it would promote survival. Why would little fish not crowd together to hide behind each other against a larger scary predator? If the fish are all packed together that formation is going to look like a ball or a column, because many fish tend to swim in circles. All of the individuals in a population are not normally exactly the same age, so there would be some emulation and adoption of whatever is furthering the successful survival of the oldest of the population. We see that in our own society, so why would that not be similar in other species? When a little calf is born or a foal or a fawn, the mother will encourage the baby animal to get right up on its feet. How does a mother know this? She knows she has to be able to run and she knows that without running there is death, so she gets her baby ready to run to ensure its survival. If the baby will not get up or will not eat heartily enough a mother will reject her baby, because she knows that baby is not going to survive anyway, so she might as well not get attached to it (sad). She has to be able to run at all times and her baby has to be able to run with her.

  2. Matt Sayre says:

    “Survival of the fittest” may be the perfect term for key aspects of evolution if like Wiktionary (http://en.wiktionary.org/wiki/fittest) you define “fittest” as “the most able to survive and reproduce in a given environment.” This definition doesn’t necessarily imply evolution as a “struggle between competing species, or a fight against the elements, wherein the strong survive, and progress.” It seems to point to structure and function that match the environment in which the organism live as simply necessary for survival. Structure and function impact the environment in that many structures allow for the function of resource extraction from an ecosystem faster than the system’s ability to regenerate that resource. This connects to co-evolution in that many species often (or thinking globally always) share ecosystem resources. Each living thing impacts others in its system and as needed and possible, new structures and functions and patterns and processes emerge allowing those living things to develop a better fit within the system or they become unable to survive. Ian does an excellent job above explaining that either structure or function comes first but that it depends on the situation. His examples make clear the possibility for either situation. I guess if I were to speculate going way back to the beginnings of life, I might conclude that on a once lifeless planet life emerged through an interaction of nonliving elements and that this interaction might be viewed as function preceding structure. Over time patterns and processes emerge and although they may not become part of one’s genetic make-up maybe these patters and processes are “coded” in another way. For example, flocks of birds follow instinctive rules that do not seem to be recorded in specific genes but the flock pattern emerges. It’s not clear to me how this pattern developed or is preserved or improved over time, but it must be a bird’s natural response to a certain environmental stimulus. And, this response must be influenced by the birds physical makeup. So, this would point back to genetic makeup as the basis for patterns and processes being preserved over generations.

  3. Matthew Burke says:

    At the population level, one mechanism of evolution is the selection of genetic varieties due to the population’s environment. In this sense, coevolution is a type of selection, as other species are part of the environment of any population. I believe coevolution is a type of selection between or among species.

    Darwin used the term “survival of the fittest”, which may have reflected the sociopolitical realities in 19th century Europe. His word choice is probably unfortunate. Contemporary thinking still seems to consider evolution as a struggle between competing species, or a fight against the elements, wherein the strong survive, and progress. If evolution is more exactly change of a population over time, then there is no inherent progress, and coevolution may be more of a dance than a struggle; on-going, always shifting balances.

    Micheal Pollan’s book “The Botany of Desire”, explains several coevolutionary examples between humans and plants: the apple tree, the tulip, marijuana, and the potato. His basic thesis is that each of these plants coevolved with humans, and it’s not exactly clear whether the plant or the human is driving the process. Both populations are selecting for each other, and both are then more successful in reproduction. Likewise, if a population of fungus, such as late blight, for example, were to affect the potato for a long period of time, this environmental stress may also affect a population of humans overly dependent on the potato. Coevolution is a process where populations affect, and are affected by other populations.

    It’s also interesting to consider how a population could coevolve with it’s ecosystem, meaning that the organisms are selecting and determining the ecosystem just as the ecosystem is selecting the organism. Perhaps it could be useful also to consider coevolution at the ecosystem level. How are ecosystems coevolving with other ecosystems? How important is it for a grassland to have a shrubland nearby, or a town to have a greenbelt nearby? Will they both be more successful together over a long period of time? Will this provide greater resilience to both in a changing climate?

    On structure and function, I can think of examples where either would precede the other, but at any given time, one or the other would probably come first. Over time, a birds beak now used for cracking seeds may also be very effective at cracking a particular beetle that is new to the region, so the bird with this structure may discover a new function and thrive. Or, a diurnal cat may be forced to do her hunting at night due to loss of quiet habitat, and over time the structure of the cat’s eyes may become modified to allow more light in during darkness.

    A gene is a bit of hereditary information that maintains consistency from generation to generation within a population, or may also mutate, leading to genetic variation. The consistency between generations of organisms is how we recognize a species. This consistency is maintained at the population level by those major constraints of evolution: inherent genetic variation, required developmental stages, limited time, and physical properties.

    The structure or pattern of a community or ecosystem may also be linked to some type of hereditary information that is passed from one community to another. Suppose we linked one forest system to another forest system, to create a new, yet distinct forest community. This new forest has very similar structure and function to the original systems, but how is the information to continue that structure recorded? I would think the populations and individual organisms themselves, behaving according to their own patterns, would provide the basic information to allow the larger pattern to sustain. The whole system would be constrained from too much deviation by the same constraints operating at the individual level. A forest does not have available the orgnisms to become a coral reef. A shrubland cannot become an old growth forest without becoming a young forest. A forest will only become old growth if allowed enough time, etc.

  4. Ian Raphael says:

    I think co-evolution fits the idea of “survival of the fittest” only to a certain point. I believe there is a critical point where co-evolution may become detrimental to the future of one or more of the organisms or the entire ecosystem they are a part of. Co- evolution may have accomplished too good of a job where niche ecological functions have become so specialized, that if distorted, throw of the entire balance of a species or ecosystem. What comes to my mind is the impact of human interference on ecosystems. The impacts are happening so quickly that species and ecosystems cannot react and adapt fast enough. A classic example of this is coral reef ecosystems. The foundation of the ecosystem started with the symbiotic relationship with coral and the algae living inside of it both giving each other nutrients to survive. This foundation has allowed for an abundant array of other species that have all co-evolved to create a very complex and specialized ecosystem. When water temperature changes or pollution drive the algae out of the coral, these coral die which causes a domino effect on the rest of the inhabitant of an ecosystem.

    So where does the idea of “survival of the fittest” fit in this scenario? Maybe each organism viewed separately has displayed all the signs of a strong evolutionary process but it doesn’t mean much if your food source disappears or your habitat is destroyed. This show the limits to evolution, where for example from the reading, a horse can’t grow wings.

  5. Monika Derrien says:

    Co-evolution helps perpetuates species-scale evolution and enlarges it onto the ecosystem scale. Organisms are reactive – and as their environments change, those that have the mechanisms and variability to change, will do so. If organisms were to exist in an entirely static environment, there would be little reason to evolve – most change would occur by genetic drift or chance. The reason organisms change is because the conditions around them present the need to fine-tune their fit with their environment. As a species evolves in close contact with another species, those species will effect each other, as they are part of the same immediate external environment within which each separate species is functioning. As one species evolves, it changes the environment of the rest of the ecosystem. Those most closely connected with that species will co-evolve out of necessity.

    I think structure and function must evolve concurrently, with each driving the other in an almost seamless way. Functions change as external influences change, and structures better suited will survive and propagate through selection. Structures will evolve, and functions will follow. At the same time, however, functions will evolve, and structures will change to serve those functions better. I would imagine it’s a game of catch-up, with function and structure taking turns leading and following.

    Patterns and processes are preserved by the mechanisms that inspire and dictate those patterns in the first place. They emerge from genetically coded behavior and traits that exist in reaction to the environments they exist in. Patterns and processes are the culmination of the interaction of thousands of evolved structures and functions. I would imagine that those organisms who are coded to have the tendency engage in some beneficial pattern that is conducive to flourishing and survival would have the evolutionary advantage.

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