New answers tagged evolution
1
Apparently, the urinary bladder is not unique to mammals, and is even found in fish, which one might presume can urinate at any time or even better - expel ammonia out of their gills, so why do they need a bladder?
I found the following article trying to understand what the bladder does in freshwater fish: https://jeb.biologists.org/content/155/1/567.
...
1
The key point you're missing is that perfection is a variable, or perhaps more accurately, a function of many variables that depend on environmental factors and the actions of other species. Even tardigrades have evolved a multitude of different species*, suited to different environments and lifestyles. And apparently they don't do all that well in hot ...
0
Why evolution do not converge on perfection? I see two main reasons:
First: the "life problem" configuration change in time, so the perfect living being (let's called it global minima) should change over time too.
Second: As the "life problem" have several dimensions and the level of complexity is huge, there's no guarantee for the existence of that global ...
2
My question is that if the aim of life in general is to ensure the continuity of the species
That is not the aim of either life or evolution. Rather individuals have the goal of surviving and genes have the aim of replicating themselves. Individuals that survive get a chance to replicate their genes.
As for why all other organisms that are not ceased ...
1
Drake's rule
Let $L$ be the size of the genome. Let $\mu$ be the average per nucleotide mutation rate, then the genome-wide mutation rate $U$ is $U=L \mu$. There is a general relationship between the genome size of an organism and the nucleotide mutation rate that makes that the genome-wide mutation rate is often approximatively 1. There is of course ...
-1
I'm sure you understand natural selection. But there are many different forms of evolution (well 4 main ones). One is based on absolute chance. For example dinosaurs were just unlucky when the asteroid struck; it wasn't as if they weren't adapted. This is called gene drift. What I'm trying to get at is that there is less than one variable that affects ...
1
A possible reason is that pigeons in a city live there year around, while urban ducks often migrate, or their populations are refreshed by new "recruits" from wild populations ; so pigeons have more opportunity to adapt to being close to people. Another possible reason is that pigeons are more agile than ducks on land and are more able to escape if you ...
1
One of the advantages of lactose in breast milk is that it is digested slower than sucrose and its ingestion results in lower fluctuations of blood glucose levels thus being a stable source of energy.
Lactose, a disaccharide of glucose and galactose, is uniquely present
in mammalian milk. Human milk provides the infant with about 40%
energy as ...
0
There are multiple definitions of complexity, ranging from algorithmic complexity to computational complexity. In biology, I'd say that algorithmic complexity (Kolmogorov complexity) is most relevant. Unfortunately, we don't yet know enough about genetic circuits and all the other things that go on at the subcellular level even to make plausible estimates ...
1
Beyond what is shown in the fossil record and in genomic analysis, the evolutionary advantage of a phenotypic feature can only be guessed at and its plausibility gauged.
That said, here's a guess that seems plausible: the sticky silk might have first served as a way to tether the caddisfly larvae to stationary rocks in a river current. The tether would ...
6
Your intuition seems fairly correct. Mouro et al 2016 show some findings relevant to your question...
Caddisflies have been around for a very long time. Much of the fossil record of their existence is of preserved shelter cases rather than the insects themselves.
Early cases seem to be made up of more variety of materials, whereas selective cases made of ...
7
How many generations are required for a specific neutral mutation to reach fixation?
Kimura and Ohta (1968) showed that the expected time for a neutral allele to reach fixation is
$$\bar t(p_0)=-4N\left(\frac{1-p_0}{p_0}\right)\ln(1-p_0),$$
where $p_0$ is the initial frequency and $N$ is the population size. The model assumes a Wright-Fisher population (...
5
Many invertebrates possess myelin. It is a misconception that invertebrates lack myelin.
The world speed record for a traveling bioelectric signal is held by the myelinated axons in the abdomen of the Penaeus shrimp!
Please take a look at this website or this review to find a highly recommended comprehensive website about invertebrate myelin from about a ...
4
Cleaner wrasse don't only clean within the mouth; although some species may specialize towards mouth-cleaning, it's likely that this behavior began with cleaning elsewhere on the fish's body.
Some studies (e.g. Bshary, 2003) suggest a large effect of cleaners on fish populations/diversity, so it seems that there are strong selective pressures for evolving ...
0
The behavior is beneficial for both species. To use your explanation, perhaps the first L. dimidiatus that was bold enough to approach C. miniata was immediately eaten, but some proportion of C. miniata did not eat the L. dimidiatus, and the alleles responsible for the cooperative behavior increased in frequency for both species, while the alleles ...
2
Have you ever tried using Mesquite?
I used it when I taught intro bio lab course as a TA.
Basically you try to come up with yes or no questions, and based on how you answer these questions it will generate a tree similar to your second link.
Can be a little bit complicated, but I am sure there are many tutorials for it on its website.
1
Its mostly due to different forms of predation.
Longer jaws are deeper and can reach farther around a prey item, it also increases the chances of catching a moving target in the jaws becasue the area the jaw covers is larger, all things being equal it should always be favored but things are rarely equal, everything has a cost. It is common to see longer ...
-2
This paper, The biomechanics of foraging determines face length among kangaroos and their relatives might provide some insight, but very likely misses a lot of factors that would apply, e.g., to wolves vs cougars. In the case of carnivores or omnivores, hunting strategies, prey capture methods, and even tearing & chewing techniques are likely to ...
2
Consider a stress: you have been bitten by a wolf, and it wants to bite you more.
Your body responds (among other things) with a surge of cortisol.
The cortisol
1: Blunts immune response. That inflamed hip you have needs to not slow you down. That chronic cough needs to go away. That stuff can wait. You need to RUN.
Blood sugar goes up. RUN!
...
0
Here are some key points about parasitoid wasp evolution:
They started radiating about 120 million years ago, at the same time as flowering plants... Today they represent 10-20% of all insect species.
They have accompanied the other insect species in their diversification since that time, and often undergo co-speciation... When a host species divides into ...
2
This has a lot to do with how development works, there is no gene that makes the nerve this long. Instead, there are genes that tell the nerve where to grow and what path to take using other tissues as landmarks. At each step of the neck getting longer letting the nerve follow this path is more beneficial than the complex evolution of pathways necessary to ...
1
I'm not sure how to address this question so that we may arrive at a suitable answer, but I'm sure that the recurrent laryngeal nerve is an example of bad design. Evolution works from traits already possessed by the parents. Mammals evolved from fishes in our evolutionary past and fishes do not have a neck. As a result the recurrent laryngeal nerve of ...
3
On a basic level, the difference in lifespan is due to the fact that the nautilus has a vastly different reproduction strategy from other living cephalopods. While most other cephalopods exhibit a rather extreme form of r-Strategy reproduction, the nautilus is, relatively speaking, a K-Strategist. To explain, r-Strategy is when a species produces many ...
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