Invertebrates Modules 1-4

What percentage of all species is invertebrates?

95%

If two branch points are the same length, what does this mean about how long those species have been evolving?

They have been evolving for the same amount of time

Population status of invertebrates

going extinct at an alarming rate

Invertebrates are model organisms for

biomedicine, genetics, and neurobiology

When did our solar system form? (including Earth) and what eon is it?

4\.6 BYA, Hadeon eon with no fossils

When was the first evidence of microbial life? and which eon is it?

3\.7 BYA, Archaean eon

When might have the first eukaryotes appeared?

2\.7 BYA

How old are the earliest fossils?

About 1.6-1.8 billion years old

Fossils form in what type of environments?

Low O2 environments like deserts and sediments in bodies of water

Low probability events for fossils to happen

material must be preserved before decomposition, rock must be exposed for discovery, someone must find it

Fossils are mostly based on what?

Morphological characters, rarely behavior and physiology

Taphonomy

the study of the fossilization process

Taphonomic bias

difference between what was once alive and its representation in the fossil record

You are more likely to find ____ fossilized material

recently

Sources of taphonomic bias

pre and post fossilization filters

Pull of the recent

the quality of the fossil record gets worse the farther back in time you look

Absolute dating

numerical dating with radioactive decay (knowing exact years)

Most fossils require ____ dating

relative (not knowing the specific age, just whether it’s old or young)

Hierarchy of time intervals

Eon > Era > Period > Epoch > Age

What are the time intervals defined by

a set of diagnostic fossils and bounded by mass extinction events

Which eon did photosynthetic bacteria/multicellular eukaryotes appear in?

Proterozoic eon

What era was the Cambrian explosion?

Paleozoic 298.9 MYA-541 MYA

What are the 5 extinctions?

Terminal-Ordovician, Late Devonian, End-Permian, End-Triassic, Cretaceous-Paleocene

Which era was the rise of mammals?

Cenozoic (era right now)

Which eon was the Precambrian?

Archean Eon

Great oxygen explosion happened in what eon?

Proterozoic

What was the great oxygen explosion?

anaerobic organisms killed off cause they were not adapted to O2

Oldest known eukaryotes are from what eon?

Proterozoic

What happened in the Phanerozoic Eon?

animals developed hard shells

Prokaryotic cells existed ____ eukaryotic cells

before

The endosymbiont theory explains

the origin of eukaryotes

Oldest eukaryotic fossils

Grypania spiralis-possibly oldest known eukaryotic alga

What are the oldest known protists?

complex unicellular bodies

What is “The Boring Billion?”

years in Proterozoic Eon between origin of Eukaryota and explosive radiation that began in the Ediacaran. First eukaryotes appeared at the start, and at the end first animals appeared

The first oxygen producing bacteria appeared in what eon?

Archean

Did the first eukaryotes appear before or after the Great Oxidation Event?

After

What does proterozoic mean?

early animal

What was in Ediacaran Period and when was it?

macroscopic animals (first evidence of animals), happened at the end of Proterozoic Eon

When is it likely that “modern life” began to evolve and why?

Paleozoic Era because of the oxygenated atmosphere

When did the first evidence for some bilaterally symmetric animals appear?

Ediacaran Period (635-541 mya)

What changes were seen in the Cambrian Explosion?

Different feeding strategies, more plants, burrowing in sand, higher diversity, predation, body parts for swimming

Chengjiang Biota Cambrian fossil site

oldest occurrences of well preserved soft and hard body animals (many arthropods)

Qingjiang Biota Cambrian fossil site

Cnidarians, annelids, and complete echinoderms appear

Burgess Shale Cambrian fossil site

dominated by arthropods

The Cambrian Explosion was marked, in part, by the evolution of?

Bilaterally symmetrical, segmented organisms. By the end, nearly all of the major, modern animal phyla had appeared

What is a possible explanation for the Cambrian Explosion?

increase in nutrients in the ocean (phosphorous and potassium)

Morphological diversity of the Cambrian Explosion

tissue types, developmental patterns, bilateral symmetry, heads\*, segmentation, appendages

How many present day animal phyla are there?

31 (most are arthropods)

The Burgess Shale is now estimated to contain fossils of how many animal phyla?

About the same number as those today

What era took out the dinosaurs?

Mesozoic

Cretaceous-Paleocene Extinction

small mammals survived, but caused extinction of 75% of all species

Likely consequences of the Chicxulub meteorite that took out the dinosaurs:

acid rain, global cooling, tsunami in Gulf of Mexico, earthquakes of huge magnitude

Why do we see an explosion of fossils from Cambrian Era?

Hard parts (exoskeletons/shells) formed which fossilize well

Linnean taxonomy ordered species how?

according to their characteristics

Hierarchical organization of larger taxonomic groups

Kingdom, phylum, class, order, family, genus, species

Which hierarchy is most specific, and which is most general?

Species is very specific whereas kingdom is very general

Taxonomy

Field of biology concerned with naming living (extant) and ancient (extinct) plants, animals, and other organisms

Phylogenetics

study of evolutionary relationships among organisms visualized with tree-like diagrams called phylogenies

Lineages with the ___ similar traits share a more recent common ancestor

most (homologies)

The more ___ the relationship among lineages, the more distinct they are from each other

distant (have had more time to evolve their distinctions since splitting from distant ancestor)

Branch point/node

represents a common ancestor, where lineages diverge

Polytomy

branch point with three taxa attached, represents unresolved pattern of divergence

Basal taxon

outgroup

Is order at the tips of a phylogenetic tree important?

No

Relatedness is determined by ____, not by the order of taxa at the tips of the tree

common ancestry

Evolutionary relationships are depicted solely by

the order of branching in a phylogeny

Proper flow of time in a branching diagram

bottom to top depicts oldest to most recent

All extant (living) species have been evolving for

the same amount of time

Long branches ___ indicate taxa with little evolutionary change

don’t

Branch length can be affected by including

more taxa in the phylogeny

Characters are used to

construct phylogenies

A character is

any attribute of an organism that can provide us with insights into evolutionary history (shared ancestry) (morphological, developmental, physiological, biochemical, genetic, behavioral)

Derived and ancestral character states

Ancestral and derived are defined relative to

a particular node in the tree

The same trait can be derived or ancestral depending on

which node is considered

Plesiomorphy

an ancestral character state (any trait that was inherited from the common ancestor of a group)

Apomorphy

a derived character state (any trait that is an innovation along an evolutionary lineage)

Shared derived homologies

Synapomorphies, homologous characters unique to a group of organisms

Synapomorphies identify

monophyletic groups (an ancestor and all of its descendants)

A group consisting of an ancestor and some, but not all of its descendants is described as

paraphyletic

A group that contains some but not all of an ancestor’s descendants and also does not contain the ancestor is called

polyphyletic

Only under extremely rare circumstances do we know

the true evolutionary history of populations or species by direct observation

A phylogenetic tree represents a

hypothesis

Homoplasy

The independent evolution of a similar character state in different taxa (a characteristic shared by different taxa, but not present in their most recent common ancestor)

Types of homoplasy

convergent evolution, parallel evolution, evolutionary reversal

Convergent Evolution

the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities (Both sharks and dolphins have similar body forms, yet are only distantly related)

Parallel Evolution

occurs when closely related taxa acquire similar characteristics

Evolutionary reversal

lineage evolves towards one of its ancestral traits, losing a more recently evolved trait

Hypoxia

condition where the body’s tissues are deprived of oxygen

How do we decide if something is convergent evolution or parallel evolution?

different species vs different populations of the same species

Evolutionary radiation

divergent evolution of numerous related lineages within a relatively short time (basically just a bunch of diverging of lineages)

Adaptive radiation

the lineages become modified for different ways of life

For molecular and genetic analysis, make sure sequences are

homologous

Orthologs

copies of the same gene in different species, related by vertical descent from a common ancestor

Paralogs

copies of the same gene within a species (ex. gene duplication), horizontal relationship as a result of gene duplication, code for proteins with similar but not identical functions

When comparing genes in phylogenetic analysis

they must be orthologous

Molecular clock

in some cases, the rate of evolution of DNA sequences is fairly constant such that sequences in different lineages diverge at a roughly constant rate (can be used to estimate age of some evolutionary events)

All animals have

eukaryotic cells that lack cell walls

All animals are

multicellular

Are animals heterotrophs or autotrophs

heterotrophs