User:Mateuszica/timeline4

This timeline give details about the common ancestor between humans and various animals.

[Category:Timelines]]

[Category:Evolutionary biology]]

User:Mateuszica/timelinetotal

User:Mateuszica/timeline









900 MYA - Proterospongia
A few living choanoflagellates, such as Proterospongia, are colonial for part of their life cycle, and show a limited degree of cell differentiation and integration into a unit; these colonial choanoflagellates are the best living examples of what the ancestor of all metazoans may have looked like.

Proterospongia is a rare freshwater protist, a colonial member of the Choanoflagellata. It consists of a number of cells embedded in a jelly-like matrix. Interestingly, it shows a very primitive level of cell differentiation, or specialization for different roles. The flagellated cells with the collar structures move the colony through the water, while the amoeboid cells on the inside divide into new cells and so help the colony grow.

Proterospongia itself is not the ancestor of sponges. However, it serves as a useful model for what the ancestor of sponges and other metazoans may have been like. Sponges also have a low degree of cell differentiation, with collar cells and amoeboid cells arranged in a gelatinous matrix; however, sponges have other types of cells, and their choanocytes beat within canals on the inside of the sponge to pull water through the sponge -- whereas Proterospongia pulls itself through the water with its collar cells on the outside, and it lacks internal canals. Nonetheless, the similarities between Proterospongia and sponges are strong evidence for the close relationship between choanoflagellates and animals.



800 MYA - Porifera
Sponges (Porifera),  and other multicellular animals appear in the oceans. system. Sponges Porifera are the phylogenetically oldest metazoan phylum still extant today; they share the closest relationship with the hypothetical common metazoan ancestor, the Urmetazoa. During the past 8 years cDNAs coding for proteins involved in cell-cell- and cell-tissue interaction have been cloned from sponges, primarily from Suberites domuncula and Geodia cydonium and their functions have been studied in vivo as well as in vitro. Also, characteristic elements of the extracellular matrix have been identified and cloned. Those data confirmed that all metazoan phyla originate from one ancestor, the Urmetazoa. The existence of cell adhesion molecules allowed the emergence of a colonial organism. However, for the next higher stage in evolution, individuation, two further innovations had to be formed: the immune- and the apoptotic system. Major defense pathways/molecules to prevent adverse effects against microbes/parasites have been identified in sponges. Furthermore, key molecules of the apoptotic pathway(s), e.g., the pro-apoptotic molecule comprising two death domains, the executing enzyme caspases, as well as the anti-apoptotic/cell survival proteins belonging to the Bcl-2 family have been identified and cloned from sponges. Based on these results—primarily obtained through a molecular biological approach—it is concluded that cell-cell- and cell-matrix adhesion systems were required for the transition to a colonial stage of organization, while the development of an immune system as well as of apoptotic processes were prerequisites for reaching the integrated stage. As the latter stage already exists in sponges, it is therefore likely that the hypothetical ancestor, the Urmetazoa, was also an “integrated colony.”

680 MYA - Cnidaria
The diverse and graceful movement of animals may have started with cnidarians ,a group that includes corals, sea anemones, sea pens and jellyfish. All of these animals, with few exceptions, have nerves and muscles. Because cnidarians are the simplest animals to possess this complexity, their direct ancestors were very likely the first animals to bundle the power of nerves and muscles together, enabling them to move and exhibit discernible behavior.

Cnidarians are also the first animals with an actual body of definite form and shape. Most of them have a simple net of neurons and no brain or nervous.

630 MYA - Flatworms


Platyhelminthes, Flatworms was the first billateral animals. they are the simplest bilateral animals today. Caenorhabditis elegans

Early forms of jellyfish seem to have evolved into various different kinds of worms, one of which was the ancestor of flatworms. They, in turn, probably evolved into higher animals. Ancestral flatworms may have first appeared around 570 million years ago. Here we see the basic plan laid out for the structure of the body which would be used and modified by all later groups of animals. Organs

Tissues (first seen in jellyfish) evolved into organs (parts of the body devoted to doing a specialized job). So, for example, they evolved a stomach. The stomach of the flatworms was just a sac. The worms took food in and send out waste through their mouths. This was not as efficient as the more advanced system we are used to, where the digestive system forms a tube with an outlet separate from the inlet! However it was a big step forward from the jellyfish. The cells of the stomach specialized in secreting digestive enzymes, making processing of food more efficient.

Brain Flatworms crawled forwards and so evolved sensors for smell and touch at their front end. An organ, the brain, developed at the front to process this information, with nerves going back to control the flatworm's body.

Bilateral Symmetry Their bodies evolved so the two sides were the same (bilaterally symmetrical). This was quite different from the radially symmetrical bodies of the jellyfish. This has been the basic design of most the higher animals. It was probably more efficient for the embryo of the worm to grow in this way rather than any other way.

585 MYA - Acorn_worm
Acorn worms are considered more highly specialised and advanced than other similarly shaped worm-like creatures. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have the gill-like structure it uses for breathing, a structure similar to that of primitive fish. Acorn worms are thus sometimes said to be a link between vertebrates and invertebrates.

570 MYA - Lancelet


The first chordates as Lancelet, pikaia.

Probably the earliest known ancestor of the chordates is Pikaia. Pikaia is the first known animal with a notocord. I'll show you a plate (pg. 34) from The Rise of Fishes by John A. Long (Johns Hopkins Press) which shows a beautifully preserved fossil of Pikaia and its reconstruction. (Long's book is superb!) The earliest known chordate or chordate-like fossils include the conodonts (cone-toothed animals). Spinar describes the conodonts as "eel-shaped animals, 4-20 cm long". "At the head end were a pair of huge eyes, and a complex basket of teeth,

505 MYA - Agnatha


Agnatha, the Ostracoderm was the first fishes (first vertebrates) Precursors to the bony fish.they was jawless such as Arandaspis.

Their internal skeletons were cartilaginous.

They lacked the paired (pectoral and pelvic) fins of more advanced fish. Prehistoric_fish

365 MYA - Sarcopterygii


Some fresh water lobe-finned fish (Sarcopterygii) develop legs and give rise to the Tetrapoda.

The first tetrapods evolved in shallow and swampy freshwater habitats, towards the end of the Devonian, a little more than 360 million years ago. By the late Devonian, land plants had stabilized freshwater habitats, allowing the first wetland ecosystems to develop, with increasingly complex food webs that afforded new opportunities.

Primitive tetrapods developed from a lobe-finned fish (an "osteolepid Sarcopterygian"), with a two-lobed brain in a flattened skull, a wide mouth and a short snout, whose upward-facing eyes show that it was a bottom-dweller, and which had already developed adaptations of fins with fleshy bases and bones. The "living fossil" coelacanth is a related lobe-finned fish without these shallow-water adaptations. These fishes used their fins as paddles in shallow-water habitats choked with plants and detritus. The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water.

The evolution of the air-breathing lung from the primitive swim bladder of lobe-finned fishes has not yet been worked out in detail. However, functioning internal gills were present in at least one late Devonian tetrapod, Acanthostega.

These earliest tetrapods were not terrestrial. The earliest confirmed terrestrial forms are known from the early Carboniferous deposits, some 20 million years later. Still, they may have spent very brief periods out of water and would have used their legs to paw their way through the mud.

315 MYA - Amphibia
Amphibia were the first four-legged animals to develop lungs]. During the following Carboniferous period they also developed the ability to walk on land to avoid aquatic competition and predation while allowing them to travel from water source to water source, and move out onto land, probably to hunt insects. Ichthyostega, Acanthostega and Pederpes finneyae. See Prehistoric amphibian.

EARLY included many Temnospondyl, Anthrachosaur, and Lepospondyl amphibians and

310 MYA - Sauropsid

 * Sauropsid Amniota

Reptiles have Advanced nervous system, compared to amphibians. They have twelve pairs of cranial nerves.

early anapsid and synapsid (e.g. Edaphosaurus) reptiles

Evolution of the amniotic egg gives rise to the Amniota, reptiles who can reproduce on land.

220 MYA - Therapsida
mammal-like reptilian

The origin of the mammals can be traced back through a series of reptilian groups called the mammal-like reptiles.

Diictodon, Cistecephalus, Dicynodon, Lycaenops, Dinogorgon and Procynosuchus, are a few of the many mammal-like reptiles known from South Africa and Russia.

This is an informal name for the reptilian group Synapsida. They evolved over an approximately 100 million year period from the Pennsylvanian to the end of the Triassic, when the first true mammals appear. The interesting feature of the evolution of the mammal-like reptiles, for our purposes, is what they suggest about how a major new group originates.

Three main phases in mammal-like reptilian evolution;

1. The first phase corresponds to one of the two major divisions of the group, the pelycosaurs. Pelycosaur fossils are preserved from the Pennsylvanian and Permian. Pelycosaurs lived there about 300 million years ago. The distinctive difference from other reptile groups is an opening in the bones behind the eye. The opening is called a temporal fenestra, and in the living animal a muscle passed through it. The muscle acted to close the jaw, and the opening up of the temporal fenestrae is the first sign of the more powerful jaw mechanism of the mammals.

2. The evolution of the therapsids makes up the second main phase of the mammal-like reptiles, in the Permian and Triassic. Therapsid fossils are found in many regions of the world. The therapsids have temporal fenestrae which are generally larger and more mammal-like than pelycosaurs; their teeth in some cases show more serial differentiation; and later forms had evolved a secondary palate. A secondary palate enables the animal to eat and breathe at the same time and is a sign of a more active, perhaps warm-blooded, way of life.

3. One sub-group of therapsids, the cynodonts (pictured opposite), make up the third phase of mammal-like reptilian evolution. The jaws of cynodonts resemble modern mammal jaws more closely and their teeth are multi-cusped and differentiated down the jaw. The cynodonts complete the story of the mammal-like reptiles, because it was from a line of cynodonts that the ancestors of the modern mammals evolved.

From synapsids came the first mammal precursors, therapsids, and more specifically the eucynodonts. Initially, they stay small and shrew-like. Constant body temperature. All mammals have milk glands for their young. One of a pair of autosomes acquires a SRY gene derived from SOX3 from X chromosome to become the Y chromosome, which has been decreasing in length since.

125 MYA - Mammals


Mammals are amniotes, and synapsids.

From synapsids came the first mammal precursors, therapsids, and more specifically the eucynodonts, 220 million years ago (mya) during the Triassic period.

Pre-mammalian ears began evolving in the late Permian to early Triassic to their current state, as three tiny bones (incus, malleus, and stapes) inside the skull; accompanied by the transformation of the lower jaw into a single bone.

Other animals, including reptiles and pre-mammalian synapsids and therapsids, have several bones in the lower jaw, some of which are used for hearing; and a single ear-bone in the skull, the stapes. This transition is evidence of mammalian evolution from reptilian beginnings: from a single ear bone, and several lower jaw bones (for example the sailback pelycosaur, Dimetrodon) to progressively smaller "hearing jaw bones" (for example the cynodont, Probainognathus), and finally (possibly with Morganucodon, but definitely with Hadrocodium), true mammals with three ear bones in the skull and a single lower jaw bone. Hence pelycosaurs and cynodonts are sometimes called "mammal-like reptiles", though this is strictly incorrect since in modern parlance these two are not reptiles, but rather synapsids.

During the Mesozoic Period mammals diversified into four main groups: multituberculates, monotremes, marsupials, and placentals.

Most early mammals were small shrew-like animals that fed on insects. However, in January 2005, the discovery was reported of two fossils of Repenomamus around 130 million years old, one more than a meter in length, the other having remains of a baby dinosaur in its stomach The earliest mammals include:


 * Eozostrodon: Triassic and Jurassic
 * Deltatheridium: Cretaceous
 * Jeholodens: mid-Cretaceous
 * Megazostrodon: late Triassic and early Jurassic
 * Triconodont: Triassic to Cretaceous
 * Zalambdalestes: late Cretaceous

Although mammals existed alongside the dinosaurs, mammals only began to dominate after the mass extinction of the dinosaurs 65 mya, in the Cenozoic.

During the next 8 million years, the Paleocene period (64–58 mya), mammals exploded into the ecological niches left by the extinction of the dinosaurs. Small rodent-like mammals still dominated, but medium and larger-sized mammals evolved.


 * Ptilodus: multituberculate
 * Pucadelphys andinus: an opposum-like marsupial
 * Purgatorius: a primate-like mammal, placental
 * Ectoconus: an early hoofed mammal, placental

Eomaia scansoria, a eutherian mammal, which leads to the formation of modern placental mammals. Looks like modern dormouse, climbing small shrubs in Liaoning, China.

65 MYA - Plesiadapis
A group of small, nocturnal and arboreal, insect-eating mammals called the Archonta branches into the primates, tree shrews and bats. Primates have binocular vision and grasping digits, features that help them to jump from one tree branch to another. One example is Plesiadapis which is extinct by 45 million years ago.

Plesiadapis is one of the oldest known primates who lived 60 mya during the paleocene on europe and north america, it looked like the moderm squirrel. Plesiadapis still had claws and the eyes located on each side of the head, because of that they were faster on the ground than on the top of the trees, but they begin to spend long times on lower branches of trees, feeding on fruits and leafs.

The characteristics that separate primates from other mammals are a large brain; the ability to grasp, which requires opposable thumbs and big toes; the ability to leap; eyes in the front of the face rather than on the side; and nails instead of claws.

55 MYA - euprimates
The earliest true primates is called euprimates. One is Carpolestes simpsoni. It has grasping digits but no forward facing eyes. Another (earliest?) euprimate Teilhardina asiatica is mouse-sized, diurnal and has small eyes and were tree-living fruit eaters.

Carpolestes combines features of the earlier plesiadapiforms with primate-like and is viewed as a transitional animal .It had very primate like teeth that were highly specialized for eating flowers, seeds, and fruit. The opposable big toe gave it a grasping ability that indicates it spent most of its time climbing trees. also had a nail on its big toe, but its eyes were not forward facing, and it did not have the bone structure that would allow for specialized leaping, like some of the earliest primates. as the diversity of fruits, flowers, leaf buds, and nectar increased in the Paleocene, 65 to 55 million years ago, Carpolestes took to the trees to exploit a new food source and to avoid competition with early rodents.

40 MYA - Prosimians
Primates (order) diverge into suborders Prosimians (a primitive monkey) and Anthropoids, the latter is diurnal and herbivorous. Examples of today's prosimians are tarsiers, lemurs, lorises.

Anthropoids, The simians (infraorder Simiiformes) are the "higher primates" very common to most people: the monkeys and the apes, including humans. Simians tend to be larger than the "lower primates" or prosimians.

The simians are split into three groups. The first division is literally as wide as the Atlantic Ocean. The New World monkeys in clade Platyrrhini split from the simian line about 40 million years ago, leaving clade Catarrhini occupying the Old World. This group split about 25 mya between the Old World monkeys and the apes. Earlier classifications split the primates into two large groups: the "Prosimii" (strepsirrhines and tarsiers) and the "Anthropoidea" (simians).

30 MYA - Catarrhini
Anthropoid (suborder) splits into infraorders Platyrrhini (New World Monkeys) and Catarrhini (Old World Primates). New World Monkeys have prehensile tails and migrated to South America. Catarrhines stayed in Africa as the two continents drifted apart. One ancestor of catarrhines might be Aegyptopithecus. New world monkey males are color blind. Anthropoids: Bugtipithecus inexpectans, Phileosimias kamali and Phileosimias brahuiorum similar to today's lemurs, lived in rainforests on Bugti Hills of central Pakistan.

25 MYA - Great apes
Catarrhini males gain color vision but lose the pheromone pathway. Catarrhini (infraorder)(Old World Primates) splits into 2 superfamilies, Old world monkeys (Cercopithecoidea) and Hominoids. The Old world monkey does not have a prehensile tail (e.g. Baboon); some do not have tails at all. All hominoids have no tails (e.g. the lesser apes, great apes and hominids).

18 MYA - Gibbon
Human ancestors speciate from the ancestors of the gibbon. Orangutans, gorillas and chimpanzees are great apes. Humans are hominids.

14 MYA - Orangutan
Human ancestors speciate from the ancestors of the orangutan. Pierolapithecus catalaunicus, Spain, common ancestor of great apes and humans.

7 MYA - Gorilla
The climate begins to dry, savannas and grasslands take over the earlier forests. Human ancestors speciate from the ancestors of the gorillas.

6 MYA - Chimpanzee
ancestors speciate from the ancestors of the chimpanzees. The latest common ancestor is Sahelanthropus tchadensis (Chad, Sahara, west of Rift Valley). The earliest in the human branch is Orrorin tugenensis (Millennium Man, Kenya).

Links
http://www.palaeos.com

http://www.ucmp.berkeley.edu

http://tolweb.org/tree