The Animal Kingdom

[popcornfrenzy]

Why do this kingdom have the highest number of known species, even on estimates? 

I know that the kingdom bacteria (and with archaea forming "monera") alone is considered the most abundant in terms of individuals and distribution around the world but I also thought that this kingdom will have the greatest diversity. I actually event thought that plants also outnumbers animals in terms of species but apparently I was wrong.

So what makes the kingdom Animalia so diverse compared to other kingdoms?

This question actually popped out of my head when I searched why animals have the greatest number of species, on which the articles that showed up only describes that this kingdom has the largest number of species and not explaining "why".

[exchemist]

3 hours ago, popcornfrenzy said:

Why do this kingdom have the highest number of known species, even on estimates? 

I know that the kingdom bacteria (and with archaea forming "monera") alone is considered the most abundant in terms of individuals and distribution around the world but I also thought that this kingdom will have the greatest diversity. I actually event thought that plants also outnumbers animals in terms of species but apparently I was wrong.

So what makes the kingdom Animalia so diverse compared to other kingdoms?

This question actually popped out of my head when I searched why animals have the greatest number of species, on which the articles that showed up only describes that this kingdom has the largest number of species and not explaining "why".

I don't know but, purely speculating, I wonder if (assuming you are right and it is true) it could be because organisms that move about can end up in a wider variety of habitats, and therefore are exposed to wider range of evolutionary pressures.

Edited March 24, 2023 by exchemist

[Genady]

3 hours ago, exchemist said:

I don't know but, purely speculating, I wonder if (assuming you are right and it is true) it could be because organisms that move about can end up in a wider variety of habitats, and therefore are exposed to wider range of evolutionary pressures.

Another speculation could be that terrestrial animals, unlike e.g. plants, don't spread their seeds far and away. This cause the animal populations being genetically isolated. This isolation leads to speciation.

[popcornfrenzy]

On 3/24/2023 at 4:37 PM, exchemist said:

I don't know but, purely speculating, I wonder if (assuming you are right and it is true) it could be because organisms that move about can end up in a wider variety of habitats, and therefore are exposed to wider range of evolutionary pressures

It could also be argued that the other kingdoms have some mode of transportation that allowed them to successfully inhabit a variety of habitats. Certain genus in the bacteria kingdom like Thermus and Geobacillus are thermopile and are able to inhabit extreme environments. Same for the variety of plants, fungi, and protists that have different dispersion strategies which allowed them to be successful in other environments. There must be a collection of factors that differentiate the rate of speciation of the kingdom animalia in comparison to other kingdoms, allowing them to have a huge variety of species. A more widespread dispersion may be one of the possible factors, but still, I think there is more to it than dispersion alone. 

23 hours ago, Genady said:

Another speculation could be that terrestrial animals, unlike e.g. plants, don't spread their seeds far and away. This cause the animal populations being genetically isolated. This isolation leads to speciation

Could be, but 100-1000m average maximum dispersal of plants is no joke too, and plants have established themselves in the terrestrial landscape long before animals did. They even colonized every continent, which allowed them to adapt to multiple types of habitat. Despite that, animals still outnumbered them in number of species. Maybe it's true that the other kingdoms are not able to spread as wide as animals, but, locomotion or transportation alone cannot explain why at a hypothetically particular set of same conditions imposed in a given area in which all the kingdoms are exposed to, animals are able to speciate into higher diversity. Isolation is also a huge factor, but it can be argued that all organisms experience isolation in varying degrees but if hypothetically the isolation is same for every organisms then won't it result to same rate of speciation for everyone?

 

I'm also curious to know that if in a simulation of a given area is populated with a single species that represents each kingdom, with enough individuals with gene variety that offsets the bottleneck effect, and they are given same amount of food or energy to consume, will the single species that represents the animals will speciate into higher diversity compared to other kingdoms overtime? 

Edited March 25, 2023 by popcornfrenzy

[Genady]

2 minutes ago, popcornfrenzy said:

if hypothetically the isolation is same for every organisms then won't it result to same rate of speciation for everyone?

But I argue that because of the mode of their sexual reproduction, populations of terrestrial animals are significantly more isolated from each other than plants or marine animals. Terrestrial male and female usually have to physically be in the same place at the same time in order to reproduce. It isn't generally so for plants or marine animals. This restriction for reproduction of terrestrial animals significantly limits gene exchange between populations. Separated populations evolve independently and become different species after a while.

[popcornfrenzy]

13 minutes ago, Genady said:

sexual reproduction, populations of terrestrial animals are significantly more isolated from each other than plants or marine animals.

The ability to sexually reproduce (exclusive for animals and higher plants) and how they sexually reproduce maybe a factor. To think that animals are more isolated than other kingdoms especially in the terrestrial environment is a huge factor for their higher diversity. 

I'm also realizing a trend here, plants and bacteria have the largest biomass on our planet; while animals have the lowest according to biomass census 

https://faunalytics.org/the-biomass-census/#:~:text=The sum of all biomass,%2C and animals – 2 gigatons. 

Both the kingdom plantae and bacteria have more individuals occupying different areas in all continent; and it's interesting to note that plants also act as a habitat (with high variety),  same for animals but mostly as coral reef in the marine. Plants can also act as vectors for isolation of other organisms, like in the Amazon where different microhabitats are created by plants alone. 

Does this mean:

The higher biomass and larger land area that the organisms occupy; the lower their species diversity is? 

[joigus]

Doesn't the question,

"Why are there so many insect/small arthropod species?"

have a heavy bearing on the OP question?

In different patches of ground in Hawaii there are different species of Drosophila alone. 416 only i Hawaii, and only in this genus.

For an insect --or any other small arthropod-- a patch of forest, or a particular layer of habitability could be in the range of meters/centimeters, etc.

Bacteria --prokaryotes in general-- are pre-sex, so... What is a species, YKWIM? Eg, are two bacteria with different plasmids the same species, and therefore expected to be subject to comparable mathematical constrictions?

[Genady]

27 minutes ago, popcornfrenzy said:

The higher biomass and larger land area that the organisms occupy; the lower their species diversity is?

There is only a handful of kingdoms. It is not statistically significant to test this hypothesis.

[dimreepr]

On 3/24/2023 at 5:06 AM, popcornfrenzy said:

Why do this kingdom have the highest number of known species, even on estimates? 

I know that the kingdom bacteria (and with archaea forming "monera") alone is considered the most abundant in terms of individuals and distribution around the world but I also thought that this kingdom will have the greatest diversity. I actually event thought that plants also outnumbers animals in terms of species but apparently I was wrong.

So what makes the kingdom Animalia so diverse compared to other kingdoms?

This question actually popped out of my head when I searched why animals have the greatest number of species, on which the articles that showed up only describes that this kingdom has the largest number of species and not explaining "why".

I don't think this is true, it seems to me that if your premise is true, it's in terms of identifiable species, as in what we can see/find; most of the planet's potential habitable zone's/place's are unknown to us, and bacteria has been found in place's that was previously considered uninhabitable.