Flashcards in Lecture 1 Deck (15):
What are the three major steps in the development of life towards animals?
Life originated about 4 billlion years ago (believed to be similar to prokaryotes)
2.1 Billion years ago the eukaryotes formed
1.5 billion years ago multicellular life began
What is the hadean era?
The era just after earth was formed 4.5 to 3.9 billion years ago when the environment was too harsh due to high temperatures and levels of volcanic and meteoric activity for life to form
What is the first evidence of life?
There is chemical evidence of life in 3.8 billion year old rocks in Issua, Greenland from an abundance of carbon isotopes which MAY be due to life
There is what is suspected to be the oldest fossil from 3.5 billion years ago seen in Western Australia which resembles some modern prokaryotes
How are prokaryotic organisms metabolically diverse?
There are autotrophs which can photosynthesize sugars, chemoautotrophs which produce energy from inorganic chemicals and heterotrophs which gain energy from organic chemicals synthesized by other animals
What are the two forms of membranes which can be seen in prokaryotes?
Respiratory membranes in oxygen breathing (aerobic forms) and thylakoid membranes in photosynthetic memebranes
What is the oldest evidence of eukaryotes?
The oldest definite fossil is 2.1 billion years old but some possible chemical fossils have been dated to 2.2 billion years ago with the earliest chemical evidence being 2.7 billion years ago
What are the two major stages in the evolution of eukaryotes/
There was an increase in size and compartmentalization
This was followed by symbiogenesis which occured at least twice to establish the mitochobdria and chloroplast
What is the evidence for the symbiogenesis generating the mitochondria?
there is similarity between respiratory membranes in oxygen breathing prokaryotes and mitochondria and thylakoid membranes and chloroplasts
both organelles also have there own DNA which is structured like prokaryotic DNA
What is the first division among the invertebrates?
The metazoa breaks into the Parazoa and Eumetazoa, with Parazoa believed to be the oldest living animals, lacking true tissues and containing only porifera (sponges) as a living phyla
What are the features of the porifera phyla?
About 9100 species and originated at least 700 million years ago
Believed to have evolved from unicellular choanoflagellates as some sponge cells are almost identical
What are the features of choanoflagellates?
They are tiny, single celled protists with a characteristic collar and flagellum and typically live in colonies
How did sponge ancestors evolve from unicellular protists?
1. There was a colonial protist aggregate of identical cells
2. There was a hollow sphere of unspecialized cells
3. There was the beginning of cell specialization with repoductive cells forming
4. There was a slight infolding in the ball of cells
5. There was gastrula like infolding forming a proto-animal with a digestive cavity
What are the common features of sponge ecology?
They are sessile or fixed in one place
All are aquatic and mostly marine (9000 marine, 100 freshwater)
They are filter feeders which use water currents to trap bacteria and small organic material from which it derives its energy
Although one species Cladorhizidae, is known to be carnivorous
What is the form of sponges (porifera)?
Have a large external size range (2m to 1cm)
resembles a sac perforated with pores (ostia) through which water flows, the body wall filters out food particles and residual water then passes into the spongocoel and returned to the environment through the osculum