Bio120 Test 2 Lec 11: Macroevolution

macroevolution

study of evolutionary processes and patterns among species

• interested in the rise and fall of biodiversity (what causes it)

• helps determine the origination of the tree of life: curious about where organisms evolved and from which ancestors they evolved from.

• interested in how traits evolve over long time scales

• showcases the rates and patterns of phenotypic evolution across time

Rise in biodiversity

periods in evolutionary history where new life forms evolved 

Fall of biodiversity

periods in evolutionary history where species die off faster than new ones evolved (extinction)

proof of macroevolutionary insights

• Paleontology

• Phylogenetics

Paleontology

• provides a direct record of past evolutionary change

• inference is strong for organisms that fossilize well (can inference their history or their past life)

• able to directly determine when certain organisms lived and where

• provides record of how evolutionary processes came to be over millions of years

• not guessing where or when an organism might have lived but fossils found in specific areas give proof of their lifestyle

Phylogenetics

• indirect record of past evolutionary change

• inference is the strongest for groups that have living representatives

• cant inference the evolutionary history of completely extinct organisms only based on phylogenetics

• can analyze the structure of phylogenetic trees to learn about the past and how species diverged as well as when

• able to know the ancestors of already living species

• good for obtaining information on organisms that do not fossilize we;; such as soft organisms

• rich with information about the relationship between organisms and knowing when past events happened

How do phylogenetics reconstruct the history of life using evidence from organisms alive today?

use phylogenetics to find patterns used in extant organisms as an inference the behaviours of extinct organisms (shared inherited features signal shared ancestry)

How old is the earth

over 4.5 billion years old

when did life evolve

about 3.5-4.1 billion years ago with the earliest evidence of a living organism being fossilized bacteria which helped determine earth's age

when did photosynthesis evolve

about 3.2-3.5 billion years ago

when did complex cells evolve

• cells that have organelles evolved by endosymbiosis about 1.8-2.2 billion years ago

• symbiosis was likely between bacteria and archaea

• sexual reproduction of single celled organisms evolved right after

when did multicellular life evolve

around 1.7 billion years ago

when did complex animal life grow

• Complex animal life grew greatly and rapidly around 540 million years ago

• this started the Cambrian explosion and marked the start of the Cambrian period

• biodiversity increased greatly

when did land plants evolve

• Land plants evolved around 470 million years ago

• dramatically transformed the terrestrial region

Cambrian explosion

when the diversity of animals picked up the pace and similar forms to today started to diverge

• started 540 million years ago

• animal diversity increase dramatically over 20-30 million years (short time with context to evolution)

• Found the first fossil appearance for most living animal phyla around this time

• First appearance of diverse body plans like skeletons, sensory organs, predation etc. 

• Started gaining defensive strategies and predatory animals

• Origins of cambrian explosion is still unknown but their was probably some environmental change and opportinitues for life to take advantage of   

Phanerozoic eon

• expands from around 540 million years ago to present

• when complex multicellular life became diverse

• a lot of fossils were found dating to around this time

• represents 10% of earths history

• 90% of life on earth was single celled

• biodiversity dramatically increased

Clades grouped into 3 major faunas during the Phanerozoic era

grouped by how successful they were during these times

• cambrian

• palaeozoic

• modern

Cambrian fauna

• organisms were the most diverse and successful following the Cambrian explosion

• following the Cambrian era the organisms died off and were replaced. They are no longer alive today

• diversity decreased

Paleozoic fauna

• dominayed the planet for 200 million years

• be