Featured Research

from universities, journals, and other organizations

UC Riverside Study Suggests Placentas Can Evolve In 750,000 Years Or Less; Guppy-Like Fish Help Fill In The Gaps In The Evolution Of Complex Organs

Date:
December 26, 2002
Source:
University Of California - Riverside
Summary:
Evolutionary biologists have long been intrigued by how natural selection -- the process in nature by which the organisms best suited to their environment are the ones most likely to survive and leave descendants -- gradually creates a complex organ such as the eye, heart, or kidney.

RIVERSIDE, Calif. -- Dec. 20, 2002 -- Evolutionary biologists have long been intrigued by how natural selection -- the process in nature by which the organisms best suited to their environment are the ones most likely to survive and leave descendants -- gradually creates a complex organ such as the eye, heart, or kidney.

Related Articles


Now UC Riverside biologists, David Reznick and Mark Springer, along with Mariana Mateos, research associate at the University of Arizona, present in the journal Science a model system for studying the evolution of complex organs. They focus on the placenta (the organ that provides nutrients for the fetus and eliminates its waste products) in the fish genus, arguing that placentas serve as a good stand-in for complex organs whose histories have eluded evolutionary biologists.

The dilemma posed by complex adaptation, which are organs of extreme complexity that have evolved through the action of natural selection, is that these organs demand contributions from a large number of adaptations at individual genetic loci to function properly. Darwin addressed the difficulty of complex adaptations with his treatment of the evolution of the eye. "He had to use organisms from different classes," explained Reznick, "because there isn't a living group of related organisms that have all the steps for making an eye." The organisms in Darwin's model are, however, distantly related to one another.

Darwin proposed that complex eyes could have been formed with a succession of photosensitive organs, each a bit more complex than its predecessor and each favored by natural selection because of the advantages that the possessor received. Visualizing such a process would be easiest if steps in this sequence were preserved in closely related living organisms; but no such sequence exists for eyes because the intermediate stages have been lost through extinction.

Reznick and his colleagues studied guppy-like fish in the genus Poeciliopsis. They report that placentas have evolved independently three times in closely related Poeciliopsis species. Other species in the genus lack placentas, and some have partial maternal provisioning via tissues that may be precursors of placentas. "Thus the fish present the full trajectory of steps involved in the evolution of this organ," said Reznick. "It allows researchers to examine what's been added, or what has changed, and eventually identify the genes associated with the evolution of each trait."

The study by Reznick and colleagues first argues that the placenta is a complex organ, in the sense that it represents a composite of many adaptations and is controlled by many genes. "The origin of complex, novel organs plays a key role in evolution since they often define new categories of animals, such as the placenta for placental mammals," said Reznick. "They are also a source of controversy both within evolutionary biology and between evolutionary biology and the religious public. This is because their origin unfolds on a time scale considerably longer than human existence, so the process must be inferred indirectly."

In the Science paper, the researchers show that:1) Fish in the genus Poeciliopsis have placentas in various stages of evolution, and 2) There are clusters of closely related species that either have highly evolved placentas, placentas in intermediate stages of evolution, or no placentas at all. These provide ideal material for studying how such complexity evolves.

The researchers then use the combination of molecular and geological data to yield estimates for how long it took the placenta to evolve in some lineages. Based on collected data, they find that the shortest time interval between a poeciliid species with a placenta and its last common ancestor without one was 750,000 years, suggesting that placentas can evolve in 750,000 years or less.

"This result demonstrates that complex organs can evolve rapidly, on the same scale as predicted by a theoretical estimate of 400,000 years for the evolution of the eye," said Springer.

Reznick has been collecting comparative life history data for around 15 years. For the study, he traveled around Latin America collecting the fish, going to museums to work with their collections, and then doing the appropriate dissections at UC Riverside. Several UC Riverside undergraduate students contributed to the dissections. Reznick also worked on live fish in his laboratory on campus.

The molecular work for the study was done by Mateos over the past two years. Springer did the phylogenetic work for the study. His statistical methods helped the researchers make inferences about how traits have evolved from the combination of DNA sequence data (collected by Mateos) and the descriptions of modes of reproduction (generated by Reznick).

The UC Riverside Department of Biology serves three main functions: undergraduate instruction, graduate education, and research in basic biology. The department conducts research and teaching in many areas of life science including cell biology, conservation biology, developmental biology, ecology, evolution, molecular biology, physiology, and population biology. The department is part of the College of Natural and Agricultural Sciences, a multi-departmental unit dedicated to instruction and basic research in the physical and life sciences, and also to 'mission-oriented' applied research in the agricultural sciences. The Biology major is a popular undergraduate major on the UC Riverside campus, with approximately 1000 students currently enrolled. Biology also provides much of the undergraduate instruction for majors in other life science departments and other science majors.


Story Source:

The above story is based on materials provided by University Of California - Riverside. Note: Materials may be edited for content and length.


Cite This Page:

University Of California - Riverside. "UC Riverside Study Suggests Placentas Can Evolve In 750,000 Years Or Less; Guppy-Like Fish Help Fill In The Gaps In The Evolution Of Complex Organs." ScienceDaily. ScienceDaily, 26 December 2002. <www.sciencedaily.com/releases/2002/12/021226071202.htm>.
University Of California - Riverside. (2002, December 26). UC Riverside Study Suggests Placentas Can Evolve In 750,000 Years Or Less; Guppy-Like Fish Help Fill In The Gaps In The Evolution Of Complex Organs. ScienceDaily. Retrieved October 26, 2014 from www.sciencedaily.com/releases/2002/12/021226071202.htm
University Of California - Riverside. "UC Riverside Study Suggests Placentas Can Evolve In 750,000 Years Or Less; Guppy-Like Fish Help Fill In The Gaps In The Evolution Of Complex Organs." ScienceDaily. www.sciencedaily.com/releases/2002/12/021226071202.htm (accessed October 26, 2014).

Share This



More Plants & Animals News

Sunday, October 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins