I have heard claims that all change in biology is sudden, but I do not know fully what is meant by that. There are events in biological systems that happen rapidly. Biochemical reactions, nerve impulses, conception, receptor binding all could be classified as sudden to a degree. Nerve impulses are still much slower than electricity travelling along a wire though.
But there are numerous examples of slower processes in biology. Starvation does not happen suddenly, though quickly in some cases. Depending on the species and the locations, migration could take a little or a lot of time. Plenty of species migrate over great distances within the frame of a season or a year. Much slower than nerve impulses.
Change in species over time is not sudden, though we do have evidence that it varies and in some instances, the evidence supports it can be very rapid geologically followed by extensive periods of stasis (little significant change).
I can think of many examples of biological events that occur at different rates from sudden to slow.
I think you would all agree that sudden needs to be defined. That is imprecise at best to claim sudden as the rate of change without even knowing what that means.
I am not arguing that some changes in living things are not relatively quick, but how can all biological change be sudden?
I propose that sudden be viewed as relative to the conditions and the time scale under discussion. Sudden in reference to evolution, for instance, is commonly on a geological time scale or over 100's, 1000's, tens or hundreds of thousands of generations. That any claim of sudden change be explained in that relation. Caution would be against making sudden, suddenly cover all time frames rendering its application useless as a descriptor of the time of change.
If anyone has evidence or different ideas about change in living things and the rate, I would be interested in seeing that explained.
The problem with answering this question is modern biology is too dependent on statistical math models which are also used by gambling casinos. It assumes mutations, which randomly appear, will be become part of the future through natural selection.
The problem is, a random change approach will do more harm than good. It will add far more negatives than positives over time, and would kill off life instead of evolve it.
As an example, have a layman rearrange the base pairs on the human genome; DNA, that is generated by a computer. Since the layman knows very little about which genes are which, and which genes do what, their colorful rearrangement of pieces will act like a source of randomness.
Next, use the computer to simulate the new DNA to see what will happen. This random approach will mess up the DNA and cause problems all over the lifeforms. The odds of any positive evolutionary change coming from this is very small. Most of the changes will causes a degrading path leading toward extinction. The casino math approach to life and evolution has to be the biggest science blunder of all time. It was disprove in the 1950's but the warnings were ignored.
I can accept the natural selection premise of evolution, but the random change approach makes no sense at all, since purely random will do more harm than good. Take your automobile apart and randomly swap its parts or add different parts everywhere, such as from other model cars. Then try to start it and drive it. You may get one set of brakes right.
A different approach to this auto scenario is to research each component that you intent to change and replace it with a better part, such as from a performance car store. You will also need to make sure the bolts align, so the new part can fit. If it does not fit, even better parts, will still be useless. Life needs a mechanism that allows choices of better parts that fit into a complex integration of existing components. This loads the dice, so the car gets better each time, we have major changes.
This mechanism is reflected on the DNA. There are certain genes that rarely change. They are so loaded random does not really apply; off limits to random activity. There are other areas of the DNA that are more variable. These dice are much less loaded, but still have some load. The current theory is too weak to explain the why's for these differences, that seems to lead all of life to upgrade, and not downgrade.
The better explanation is needed for not only for evolution, but also for the observation of thriving and healthy life, everywhere. This approach is connected to the concept of entropy.
Any given state of matter defines a fixed amount of entropy. This is an engineering principle. This can be measured in the lab and is not an abstraction. The second law states that the entropy of the universe also has to increase over time. This is why we cannot have perpetual motion.
Life is based on a wide range of states of matter, from organelles, to cells, to organs, with each state having a fixed amount of entropy, with this entropy increasing over time via the 2nd law. An evolutionary change, means there is a natural push; 2nd law, for lower states to move into states of higher entropy; new state.
We also live in a quantum universe, where only distinct states are possible, with gaps between these distinct states. As cellular entropy increases, there will be gaps between the next entropic states, before we see any quantum jump into the next quantum states. This is observed as missing links. We will not see anything happening in the gaps, until the gap is transversed. The gap is more of a retrofitting period. When a new quantum state finally appears, it is then subject to natural selection.
In terms of entropic states, water at 25C and 1 atmosphere has a measured entropy value of 188.8 Joules/(mole K). This is measured the same in all labs. The entire state of all these 6.02 x1023, water molecules, all interacting, adds to this constant amount of entropy. This is very profound.
Science will model a mole of water; 6.02 x 1023 molecules of water, as all interacting in various random ways; very complex. Although we use randomness to model all the water molecules, the sum of all that assumed randomness always adds to a constant; 188.8 Joules/(mole K). What appears to be random, based on theory, actually has an order that always has to add to a constant. Determinism; constant entropy, leads all the apparent randomness. The randomness is deterministic.
In terms of states of matter, such as a cell, what appears to be random changes on the DNA, is actually balancing out other changes in the cell, often due to changes in environmental input, so the entropy value of the entire cellular state can stay constant, increase in the gap, even increase to the next quantum state. This makes sense, since change needs to be connected to balancing and optimizing need; choosing the correct high performance brakes that fit the car based on the new role the car is expected to play.
In the Galapagos Island, where Darwin wrote his Origin of Species, change was very slow. Life stayed the same over a long period of time. This tells us that environmental potential play a role in evolution. If the environment is constant, change will be slow. There is little new push for change. Life change does not just randomly happen, but waits for the potential of need. The entropic state is the whole life form, and not just the DNA. The protein grid of the cell can increase entropy with little impact on the DNA.
The Cambium explosion was the opposite where the diversity of life changed quickly. This appears to have been connected to rapid changes in the external environment potentials. This added lot of entropy to life; 2nd law, which then pushes the states of life, into higher quantum states, again and again.