Ectasian
Encyclopedia
The Ectasian is the second geologic period in the Mesoproterozoic
Era and lasted from 1400 Mya ago to 1200 Mya (million years ago). Instead of being based on stratigraphy
, these dates are defined chronometrically.
Name derives from continued expansion of platform cover
s during this period.
This period is interesting for the first evidence of sexual reproduction. The 1.2 billion year old Hunting Formation on Somerset Island, Canada
, dates from the end of the Ectasian. It contains the microfossils of the multicellular filaments of Bangiomorpha pubescens (type of red algae
), the first taxonomically resolved eukaryote. This was the first organism that exhibited sexual reproduction, which is an essential feature for complex multicellularity. Complex multicellularity is different from "simple" multicellularity, such as colonies of organisms living together. True multicellular organisms contain cells that are specialized for different functions. This is, in fact, an essential feature of sexual reproduction as well, since the male and female gametes are specialized cells. Organisms that reproduce sexually must solve the problem of generating an entire organism from just the germ cells.
So long as reproduction simply means one cell copying itself, true multicellularity cannot exist. Therefore, sexual reproduction and the ability of gametes to develop into an organism is the necessary antecedent to true multicellularity. In fact, we tend to think of sexual reproduction and true multicellularity as occurring at the same time, and true multicellularity is often taken as a marker for sexual reproduction.
Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...
Era and lasted from 1400 Mya ago to 1200 Mya (million years ago). Instead of being based on stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
, these dates are defined chronometrically.
Name derives from continued expansion of platform cover
Platform cover
In geology, a platform cover is the sedimentary and volcanic deposits that lie on top of a craton....
s during this period.
This period is interesting for the first evidence of sexual reproduction. The 1.2 billion year old Hunting Formation on Somerset Island, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, dates from the end of the Ectasian. It contains the microfossils of the multicellular filaments of Bangiomorpha pubescens (type of red algae
Red algae
The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000–6,000 species of mostly multicellular, marine algae, including many notable seaweeds...
), the first taxonomically resolved eukaryote. This was the first organism that exhibited sexual reproduction, which is an essential feature for complex multicellularity. Complex multicellularity is different from "simple" multicellularity, such as colonies of organisms living together. True multicellular organisms contain cells that are specialized for different functions. This is, in fact, an essential feature of sexual reproduction as well, since the male and female gametes are specialized cells. Organisms that reproduce sexually must solve the problem of generating an entire organism from just the germ cells.
So long as reproduction simply means one cell copying itself, true multicellularity cannot exist. Therefore, sexual reproduction and the ability of gametes to develop into an organism is the necessary antecedent to true multicellularity. In fact, we tend to think of sexual reproduction and true multicellularity as occurring at the same time, and true multicellularity is often taken as a marker for sexual reproduction.