How did Animals Evolve to Live in Colonies?
Summary
TLDRCe script explore l'évolution paradoxale des colonies animales, comme les fourmis et les abeilles, où les individus peuvent sacrifier leur reproduction pour l'avantage du groupe. Il explique comment la sélection naturelle, en particulier la sélection de parenté, a favorisé l'apparition de castes et d'un altruisme reproducteur. Les Hymenoptères, avec leurs huit évolutions distinctes de colonies sociales, illustrent cette adaptation, où les mâles sont produits sexuellement et les femelles asexuellement, créant un fort investissement dans la réussite reproductive des autres membres de la colonie.
Takeaways
- 🐝 Les animaux évoluant vers la vie en colonies semble paradoxal car ils vont à l'encontre de la sélection naturelle.
- 🐜 Les insectes comme les fourmis et les abeilles vivent dans des colonies sociales où les ouvriers aident à la réussite reproductive des autres membres.
- 🌟 Charles Darwin a considéré l'évolution des colonies animales comme un problème majeur pour sa théorie de l'évolution.
- 🔄 Les colonies animales se définissent par trois principes : habiter ensemble, s'occuper des jeunes et l'altruisme reproductive.
- 🐝 L'ordre des Hymenoptères (abeilles, guêpes, fourmis) offre des exemples de colonies sociales qui se sont développées à plusieurs reprises.
- 🐜 D'autres animaux comme les termites, les charançons et même des crustacés ont également évolué pour former des colonies sociales.
- 👥 Les colonies sociales ont souvent des systèmes de castes avancés avec des rôles spécifiques et des corps adaptés pour chaque tâche.
- 🌱 Certains animaux sociaux évitent l'inbreeding en envoyant des individus spécifiques (dispersés) chercher des partenaires à l'extérieur de la colonie.
- 👪 La sélection de parenté (kin selection) est un type de sélection naturelle où les animaux peuvent aider la réussite reproductive de leurs proches parents pour assurer la survie de leurs propres gènes.
- 🐝 Chez les Hymenoptères, les mâles sont produits sexuellement et les femelles sont issues d'un œuf fécondé, ce qui crée une pression selective pour l'aide à la reproduction des autres membres de la colonie.
- 🌿 Les colonies sociales se forment souvent autour de la collecte de ressources dispersées ou la défense de ces ressources.
Q & A
Pourquoi la vie en colonies semble-t-elle contredire la sélection naturelle?
-La sélection naturelle par Darwin suggère que les animaux devraient se combattre pour transmettre leurs gènes. Cependant, dans les colonies, les animaux tels que les fourmis et les abeilles aident à la réussite reproductive d'autres membres, voire sont stériles, ce qui peut sembler aller à l'encontre de la sélection naturelle.
Quels sont les trois principes qui définissent une colonie sociale d'insectes?
-Les trois principes sont: vivre en un lieu unique, généralement un nid, s'occuper des jeunes des autres, et pratiquer l'altruisme reproductive où les travailleurs aident à la réussite reproductive des autres membres de la colonie.
Pourquoi les Hymenoptères sont-ils un exemple exceptionnel de colonies sociales?
-Les Hymenoptères, qui incluent les abeilles et les fourmis, se sont développés en colonies sociales à plusieurs reprises, illustrant la convergence évolutive et la complexité des castes et des rôles au sein de ces colonies.
Quels sont les autres animaux qui vivent en colonies sociales autres que les insectes?
-Des animaux comme les termites, les charançons, le shrimp Sein Alpheus et certains mammifères comme les taupes et les rats des taïgas vivent également en colonies sociales.
Comment l'altruisme reproductive est-il expliqué par la sélection naturelle?
-La sélection naturelle peut inclure le kin selection, où les animaux peuvent aider la réussite reproductive de leurs proches因为他们 partage beaucoup de gènes communs, donc en aidant leurs proches, ils assurent indirectement la survie de leurs propres gènes.
Quels sont les avantages évolutifs de la vie en colonies pour les ressources dispersées?
-Les colonies permettent de partager et de défendre des ressources qui sont éparpillées et rares, offrant un avantage aux animaux de rester groupés plutôt que de vivre seuls.
Pourquoi les Hymenoptères ont-ils tendance à éliminer les mâles dans les temps difficiles?
-Les femelles des Hymenoptères partagent seulement 25% de leurs gènes avec les mâles produits sexuellement, ce qui rend les mâles moins importants pour la survie génétique de la colonie.
Quels sont les exemples d'adaptations physiques dans les colonies d'insectes?
-Les fourmis peuvent avoir des têtes et des mâchoires massives pour protéger la colonie, tandis que la reine peut être dix fois plus grande que les ouvrières pour assurer la reproduction.
Quelle est la signification de la détermination du sexe chez les Hymenoptères pour la formation de colonies?
-Comme les mâles sont produits par reproduction sexuelle et les femelles par reproduction asexuée, les femelles partagent 75% de leurs gènes avec leurs soeurs, créant une pression selective pour aider la mère à reproduire plutôt que de reproduire elles-mêmes.
Quels sont les exemples d'innovations évolutives dans les colonies d'insectes?
-Certaines fourmis comme les fourmis coupeuses de feuilles ont développé une forme d'agriculture en cultivant des champignons, ce qui a pu se produire il y a au moins 30 millions d'années.
Quel rôle jouent les colonies sociales dans l'écosystème?
-Les colonies sociales sont cruciales pour l'écosystème, pollinisant les plantes, aérant le sol et fournissant de la nourriture à de grands insectivores.
Outlines
🐜 Évolution des colonies animales
Le premier paragraphe explore l'évolution paradoxale des animaux vivant en colonies, en particulier les insectes comme les fourmis et les abeilles qui pratiquent l'altruisme reproducteur. Malgré le principe de sélection naturelle, ces animaux peuvent être stériles et aider à la réussite reproductive d'autres membres de la colonie. Charles Darwin a reconnu cette évolution comme un problème pour sa théorie. Les colonies sociales sont définies par trois principes : habiter ensemble, s'occuper des jeunes et l'altruisme reproducteur. Les Hymenoptères, comme les abeilles et les fourmis, en sont les meilleurs exemples, mais d'autres animaux comme les termites et les scarabées forment aussi des colonies. Ces colonies évoluent souvent avec des systèmes de castes avancés, où les membres ont des corps de tailles et formes différentes pour effectuer des tâches spécifiques.
🧬 Sélection de parenté et colonies animales
Le deuxième paragraphe traite de la sélection de parenté, une forme de sélection naturelle où les animaux peuvent évoluer pour aider la réussite reproductive de leurs proches parents, avec qui ils partagent de nombreux gènes communs. Une étude sur les écureuils roux a montré que ce comportement est courant chez de nombreuses espèces de mammifères. La théorie de l'hypothèse monogame suggère que les animaux monogames ont des enfants qui sont du même degré de parenté avec leurs frères et soeurs qu'ils sont avec leurs propres enfants, créant une pression de sélection pour aider les parents à se reproduire. Les Hymenoptères, avec leur mode de détermination du sexe basé sur la fertilisation, ont un taux de partage de gènes élevé avec leurs frères et soeurs, ce qui crée une pression de sélection pour la réussite reproductive des autres membres de la colonie.
🌿 Rôle des colonies animales dans les écosystèmes
Le troisième paragraphe souligne l'importance des colonies animales dans les écosystèmes. Les colonies sont souvent centrées sur l'extraction de ressources dispersées, ce qui favorise leur évolution. Par exemple, les termites dépendent de bois pourri et les rats des tubercules qu'ils creusent. Ces ressources nécessitent d'être défendues, ce qui est plus efficace en étant en colonie. Les Hymenoptères, qui sont généralement des charognards ou qui fabriquent leur propre nourriture, pourraient avoir évolué des colonies pour se défendre contre les prédateurs. Les colonies sociales sont apparues pour la première fois à la fin du Crétacé et peuvent être plus anciennes. Les insectes, comme les abeilles et les fourmis, ont évolué des adaptations pour la collecte de pollen et la domestication de champignons pour leur nourriture. Les colonies animales sont essentielles pour de nombreuses créatures qui dépendent d'elles pour la pollinisation et la fertilisation du sol.
Mindmap
Keywords
💡Colonies
💡Sélection naturelle
💡Altruisme reproductive
💡Hyménoptères
💡Castes
💡Kin selection
💡Monogamie
💡Ressources
💡Co-évolution
💡Extinction
Highlights
Animals evolving to live in colonies seems paradoxical to natural selection.
Workers of ants or bees help reproductive success of others and are often sterile.
Charles Darwin considered the evolution of animal colonies a problem for his theory.
Social animals like humans, elephants, and wolves live in colonies.
Insects like ants and bees live in huge social colonies defined by three principles.
Colonies are characterized by living in one place, caring for young, and reproductive altruism.
Hymenoptera, the order containing bees and ants, offers the best examples of these colonies.
Colonies have evolved multiple times in Hymenoptera.
Non-insect animals like snapping shrimp and mole rats also form colonies.
Colonies share features like advanced caste systems and division of labor.
Kin selection explains how animals help close relatives, ensuring survival of their own genes.
Monogamous animals have a stronger selective pressure to help their parents reproduce.
In Hymenoptera, males are produced asexually, leading to a higher relatedness with siblings.
Eusocial colonies are centered on extracting resources with a patchy distribution.
Ants and bees may have evolved colonies to better defend their nests from predators.
Fossil evidence suggests bee and wasp colonies first appeared in the late Cretaceous.
Some ants have developed agriculture, domesticating a unique fungus species.
Eusocial colonies play a crucial role in ecosystems, aiding in pollination and soil aeration.
Transcripts
animals evolving to live in colonies
seems to be a paradox flying in the face
of the core components of evolution by
natural selection whereas many species
of animals will fight one another to
pass on their genes the workers of ants
or bees will actively help with the
reproductive success of other members of
the colony and are often even sterile to
have evolved to be unable to pass on
their genes Charles Darwin even
considered the evolution of animal
colonies that do this to be a major
problem for his theory so how did some
animals start helping other animals pass
on their genes
technically all social animals like
humans elephants and wolves live in a
sort of colony but the type of colony
that insects like ants and bees live in
are known as huge social colonies and
these types of colony are defined by
three principles the animals live in one
place most commonly in some sort of nest
caring for each other's young and most
importantly reproductive altruism where
the workers will aid in the reproductive
success of other colony members
Hymenoptera the order of animal that
contains bees and ants offer the best
examples of these types of colonies
because it has evolved as many as eight
separate times in this group however
these types of colonies are by no means
contained among Hymenoptera as termites
and weevils also form these types of
colonies but it's also some non insects
do as well there is a type of snapping
shrimp called Sein Alpheus regardless
the form societies consisting of a queen
and as many as 300 individuals that
protect and feed on a type of sponge and
even some mammals live like this as mole
rat burrows only have one female and one
to three males that reproduce while the
rest of the members of the colony are
sterile and function as workers eating
and gathering tubers from the ground so
colonies have convergently evolved on
many occasions but also these colonies
share many other features as well many
having advanced caste systems where they
divide labour up among different members
of the colony that have different body
sizes and shape to help them with their
appointed tasks this is very well
demonstrated among Hymenoptera where the
Queen can be twenty times the size of
the regular workers and sometimes ants
have soldiers that guard the workers
while they are gathering resources that
have massive heads and jaws but nearly
all you social animals have evolved
different castes within their colonies
termites also have convergently evolved
very similar castes ants of soldier
termites but even mole rats have castes
if nowhere near is pronounced as with
ants and termites some members of the
mole rat colonies are known as disperses
that will leave the colonies to find a
mate from another colony to stop
inbreeding these individuals are
distinct from the other members of the
colonies as they usually have more fat
reserves for the journey and are only
interested in mating with individuals
from foreign colonies so this is an
evolutionary pathway that is very common
once animals have evolved into a colony
that is not really seen in any other
types of animals use social colonies are
confusing but they do not define natural
selection as much as you might think
since the 60s it has been argued that
there is a type of natural selection
called kin selection where animals may
evolve to help with the reproductive
success of their close relatives because
they will share a lot of the same genes
and so by helping close relatives they
are actually ensuring the survival of
their own genes just indirectly a study
in 2010 conducted on red squirrels
supported this red squirrels sometimes
adopt orphan squirrel pups and it was
found that they will only do this when
the squirrel pup is a close relative and
this sort of behavior is known across
many species of mammal looking after
their close relatives would mean that
there is more of a chance for the
squirrels genes to survive and so there
would be a Selective pressure for the
squirrel to start caring about the
survival and reproductive success of
their close relatives this would show
how kin selection may have played a part
in the evolution of nearly all social
animals who use social animals took this
a step further in most cases animals
will have siblings that vary in
relatedness because animals usually mate
with several different individuals
throughout their life
however in monogamous animals that only
have one may throughout their life all
of their children will be of the same
relatedness to their siblings as they
are to their own offspring this would
imply kin selection because the animals
would be just as likely to pass all
their genes with their own offspring as
they would be with the reproductive
success of their parents
meaning the Selective pressure to
reproduce would be just as strong as
helping their parents reproduce and this
could be how you social groups got
started and is known as the monogamous
hypothesis as explained Hymenoptera have
organized themselves into colonies on
many different occasions and this may be
because of their very strange way of
determining sex in their offspring a
fertilized egg from an ant or a wasp
will produce a female but if the egg is
left unfertilized it will produce a male
meaning the males are reproduced
asexually this is important because it
means that male Hymenoptera only have
one set of chromosomes whereas female
ants have two like other animals so this
means that unlike other animals that are
equally related to their parents and
offspring as they are to their siblings
I were not reshef 50% of their genes
with their mother and offspring like
most animals but share 75% of their
genes with their siblings this means
that they actually pass on more of their
genes from helping their mother
reproduce more siblings than if they
would produce offspring themselves
creating a big selective pressure for
the reproductive success of other
members of the colony and explains the
abundance of eusocial colonies among
Hymenoptera adding to this many species
of bees will invest less in or even kill
male members of the colony when times
are tough which makes sense seeing as
the female bees will only share 25% of
their genes with the a sexually produced
males eusocial colonies are also usually
centered on extracting a resource that
has a patchy distribution which may be
important for their evolution for
instance termites rely on rotting and
decaying wood naked Mallrats rely on
eating tubers that they dig in their
burrows and the snapping shrimp that
live in colonies rely on a type of
sponge as these resources are focused in
certain spots and are far and few
between the animals would be
disadvantaged to leave as individuals
because they may not be able to find
other resources but would benefit from
forming colonies and sharing the
resource and also these resources would
need to be defended which they would
have a lot more success doing if they
could band together
the exception to this is Hymenoptera
that are usually scavengers or make
their own food and do not rely on a
singular resource that needs protecting
however they may have originally bounded
together to defend their colony from
predators there are species of solitary
be like mason bees that are not used
social that make nests near one another
sometimes even making their nests
communally the key to themselves and
look after their young individually the
benefit of this seems to be that it's
easier to defend their nests from
predators so this may have been what
kick-started the evolution of colonies
in ants and bees if not a singular
resource
hiren Optra have not just organized
themselves into colonies the most amount
of times but they will also wonder the
first known groups of animals to live
this way aunt bee and wasp colonies are
thought to have first started to appear
in the late cretaceous but may have
evolved a lot longer ago than this and
as you social colonies have evolved on
so many separate occasions it is
possible that there may have been other
insects that evolved into colonies
before this but have gone extinct in
northern Myanmar there is a large amount
of amber that dates back to around 99
million years ago that has yielded many
interesting animals like ancient birds
lizards frogs and even a dinosaur tail
however one of the most abundant ancient
animals to find in the amber are insects
and one of the discoveries was of a
hundred million year old bee that was
covered in pollen and had made
adaptations for pollen collection and
carrying there are also ancient ants
that have been found in amber from the
same time period ants and bees evolved
from wasps and during the Cretaceous at
the time when these insects were at
large it would have been when they had
just diverged from them and this can be
seen in these ancient ant specimens that
have many wasp features that modern ants
do not have because they may have lost
them since the Cretaceous because some
ants have been living in new social
colonies for so long they have evolved
some of the most advanced ways of
finding or even growing food as some
species of ants like leaf cutting ants
developed agriculture and this may have
happened at least 30 million years ago
30 million years before humans leaf
cutting ants don't eat the leaves they
cut from parts they feed it to a fungus
they farm and then eat the fungus it is
thought that this started because the
ants may have bought an infected leaf
and the fungus was able to spread to the
other leaves as ants often store their
food for some period of time before
consuming them and as this became a good
food source for the ants they started to
switch to eating the fungus instead of
the leaves the interesting thing is that
these ants have been doing this for so
long that the fungus they eat is a
unique species of fungus not found in
the wild so they have domesticated their
own crop and the ants are so strongly
linked to it the many species of Queen
that go out to form another colony carry
a pellet of fungus with them that they
used to start growing the first food for
that new colony around 35 million years
ago South America started to become a
lot drier this would have meant that the
wild fungus would have retreated leaving
the fungus in the ant colonies that
lived in dry habitats isolated so it
could develop on its own and develop
into its own species this would have
been a similar process to humans taking
crops out of the wild and isolating them
so they can be domesticated now the
fungus relies on these ants because they
have co-evolved and in fact there are
many animals and plants that rely on use
social colonies as there are many large
insectivorous creatures that probably
couldn't find enough sustenance and less
large colonies of insects existed and
now many plants are reliant on
pollination from bees and ants aerate
the soil allowing water and oxygen to
reach plant roots so you social colonies
aren't just a strange outcome of
evolution but since the dinosaurs have
been around have been one of the most
important animals in the world's
ecosystems thank you for watching a big
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