Lecture 3 - Speciation II, History of Life on Earth, Intro to Animal Diversity, Invertebrates I Flashcards
How old is earth?
4.5 billion years
How long has life existed on earth?
How long has human civilization been around?
~ 3.8 billion years
.0003% of history of life
How is the history of life conceptualized/organized?
Eras - Separated by catastrophic extinction boundaries
Periods - Subdivide eras
Differences in fossils in successive layers of rock
Pre-Cambrian
- Super eon
- origin of life
- first 4 billion years of earths existence
Precambrian to cambrian transition
- “explosion” of new life forms
- just over .5 billion years ago
Physical events that have contributed to nature and timing of evolutionary changes among organisms (5)
- Continental drift
- atmospheric oxygen concentrations
- climate
- volcanoes
- extraterrestrial events (ex. meteorites)
Continental Drift
- Earths crust consists of several plates 40km thick, floating on fluid layer of magma
- Heat creates convection currents which exert pressure on plates
- Move apart or together
- Formation, size and position of continents
- Oceanic circulation patterns, global climate, sea levels
Himalayan Mountains
Ex: of continental drift
- Tallest range in world
- Created by Indian and Eurasian continental plates colliding
- Collision caused plates to buckle and get pushed upwards
- Himalayas continue to rise more than one cm a year
Super-Continents
List them:
- Caused by continental drift
- Most recent super-continent was Pangaea
- Believe that in 250 million years all continents will reform as one again
- Ur
- Kenorland
- Columbia
- Rodinia
- Panhotia, Gondwana
- Pangaea
- Next super continent
Fossil Configuration and Continental drift
- Fossil patterns in different continents show how they were connected
Continental Shift and Species Survival
What doe is affect? (3)
- Shifting affects:
1. oceanic circulation patterns
2. global climates
3. sea levels - Major drops in sea levels have usually been accompanied by massive extinctions, especially of marine organisms
Atmospheric Oxygen Concentrations
timeline
- have changed over time
- 2 major increases in oxygen
- 1 major decrease
Timeline:
- ~2 billion years ago: 1st photosynthetic bacteria
- 750 mya - first increase
- ~400 mya - second increase
- 250 mya - decrease = great dying
First oxygen increase
What did it allow?
- certain bacteria evolve ability to use water in photosynthesis. Oxygen released as a waste
- Prokaryotes could evolve aerobic respiration
- Advantages - aerobic metabolism proceeds more rapidly and harvests more energy than anaerobic
- aerobes replaced most anaerobes
- made possible: larger cells and more complex multicellular organisms
Second Oxygen Increase
What did it allow?
- oxygen increased during carboniferous and permian periods
- evolution of large vascular plants in lowland swamps
- oxygen was 50% higher than today
- allowed evolution of giant flying insects that wouldn’t survive in today’s atmosphere
Drop in Oxygen
- drying of swamps cause rapid drop in oxygen concentrations
- “the great dying”
- mass extinction of 96% of earth’s species
diversification of flowering plants helped gradually rebuild oxygen concentrations
Climate Change
- Earth was often considerably warmer than today
- Sometimes colder with extensive claciation
- Range of average temps has spanned 10c or 18F
- cold periods separated by long periods of milder climates
- Short period of major climatic shifts: 5 - 10k years
- Rapid climate changes typically lead to extinctions
Volcanoes
- Many volcanic eruptions when the continents came together to form Pangaea in Permian period
- occurred as continents drifted apart during the late Triassic and end of Cretaceous periods
- Large volcanic eruptions inject ash ans sulfur dioxide into atmosphere –> leads to Sulphurous acid that blocks sunlight
- Causes drop in temperature glaciations
- potentially responsible for several mass-extinctions
- Likely contributed to drying of swamps and killing of plants that caused “great dying”
Extraterrestrial Events
- Collision with large meteorites cause of mass extinctions
Ex:
- End of mesozoic period - end of dinosaurs
- 180km crater located in mexico
- = 100 million megatons of high explosives
- plume of debrisheated atmosphere, ignited fires, blocked sunlight
- settling debris formed iridium rich layer
Date of Lower sea levels and glaciation mass ext.
444 million yrs ago
Date of “great dying”
251 million yrs ago
Date of Yucatan meteorite
65.5 million yrs ago
When was the first life?
When were the first eukaryotes?
Precambrian Era
- first evolved about 3.5 - 3.8 billion years ago
- mostly microscopic prokaryotes
- Eukaryotes evolved part way through
- 1.5-2.1 billion years ago
2 Major Events that set the stage for rapid diversification of Life that occurs upon entry into Cambrian period
- Evolution of Eukaryotes
2. Increasing oxygen levels
Cambrian Explosion
- Begining of Paleozoic Era (542-488 mya)
- Oxygen levels approaching current level
Rapid Diversification of Live in Cambrian Explosion
- # individuals and species increased dramatically in the late Precambrian into the Cambrian
- Many of the major groups of animal species seen today first evolved during the Cambrian
- Largely or completely aquatic during this time
- Foundation for most major Phyla of organisms was created
- then tweaking, radiating, evolving groups of life
Diversity of Species in Remainder of Paleozoic
- more complex aquatic species developed
- colonization of land, early amphibians and insects
- mass extinction killed 96% of species
Radiation of Reptiles and Mammals in Mesozoic and Cenozoic
Mesozoic:
- Age of reptiles, including dinosaurs
- first mammals appear (small)
- mass extinction kills most species over ~50lbs
Cenozoic:
- Extensive radiation of terrestrial vertebrates and flowering plants
- Especially mammals
Three domains of life
Archaea, Prokarya and Eukarya
Archaea more closely related to eukarya
have a common ancestor, after the common ancestor with prokarytes
Characteristics of Animals
- Multicellularity
- complex patterns of dev
- no cell walls - Heterotrophic Metabolism
- must take in nutrients from their environment - Internal Digestion
- most habe internal gut which digestion breaks down molecules from environment into the organic molecules the animal needs - Movement and Nervous System
- most can move
- coordinated through nervous system
- muscle tissue
Ancestor of Animals
- colonial flagellated protist related to choanoflagellates
- colony = individual members of a species living closely together toward mutual benefit, but can survive if separated on their own
- certain cells began to become specialized
- evolve into multicellular organisms with specialized cells
Major derived traits
“umbrella pattern”
- Eumetazoa vs Sponges
- Tissue vs no tissue
- Diploblastic vs Triploblastic
- Tissue
- 2 embryonic cell layers vs 3
- Protostome vs Deuterostome
- Tissue
- 3 embryonic cell layers
- Mouth forms first vs anus forms first
Acoleomate, pseudocoelomate and coelomate
- protostomes and deuerostomes
Eumetazoa vs Sponges
- First Derived Trait - Distinct tissues
- Tissues: Collection of specialized cells isolated from other tissues by a membrane (epithelial, muscle, etc)
- Sponges have NO distinct tissue types, just specialized loosely arranged cells
- ALL other animal groups are Eumetazoans, “True Animals”
- Obvious body symmetry, gut, nervous system, tissue organized into distinct organs
- Must have at least 2 embryonic cells layers (endoderm and ectoderm) to give rise to tissues
Diploblastic vs Triploblastic
Radial vs Bilateral Symmetry
Diploblastic Animals
- 2 embryonic cell layers (ectoderm outside, endoderm inside)
- Radially Symmetrical
- Body parts around one main axis (ex: comb jellies, corals, jellyfish, sea anenome)
- Sedentary, shift with currents or move very slowly
Triploblastic Animals (Bilaterians)
- 3 embryonic cell layers (ectoderm, medoderm in middle, endoderm)
- Bilateraly symmetrical
- cannot be divided into mirror image have by single plane through midline
- distinct front end and planes: anterior/posterior; dorsal/ventral; left/right
- correlated with cephalization (conc. of nervous tissue in head)
- Exception: Echinoderms/starfish (adults are radial, larvae are bilateral_
Protostome vs Deuterostome
- Blastomere development in mouth and anus
- 2 major triploblastic clades
Protostomes
- blastopore becomes mouth
- anus arises later
Deuterostomes
- Blastopore becoems anus
- mouth forms later
Examples of Protostomes
- arrow worms
- Lophotrochozoans (flatworms, annelids, mollusks)
- Ecdysozoans (nematodes, arthropods)
Examples of Deuterostomes
- Echinoderms (starfish, sea urchins)
- hemichordates (acorn worms)
- Chordates (vertebrates)
Coelom
- fluid filled body cavity
- endoderm forms the gut
- ectoderm froms outer layer, skin
- mesoderm in middle surrounds cavity
Roles:
- cushion internal organs
- provides hydrostatic skeleton to support the organism and allow it to bend and move
- allow organs to expand
Ways Coelm can be organized
- Acoelomate
- Pseudocoelomate
- Coelomate
Acoelomate
- lack an enclosed fluid-filled body cavity
- mesoderm forms solid mass in contact with both endoderm and ectoderm
- animals move by cilia
Pseudocoelomate
- animals have fluid-filled space in which many internal organs are suspended
- Enclosed by mesoderm (muscle) only on the outside (in contact with ectoderm)
- no inner layer of mesoderm surrounding internal organs (not in contact with endoderm)
Coelomate
- Animals have a body cavity that develops within the mesoderm
- Coelom is enclosed on both inside and outside by mesoderm
- all deuterostomes are coelomates
Can protostomes be coelomates?
Yes, all three
Major Groups of animals
- Sponges/Porifera
- Diploblasts
(ctenophores, cnidarians) - Triploblasts/Bilaterians
(protostomes, deuterostomes)
Sponges
- simplest animals
- no distinct embryonic cell layers, no true organs
- lack body symmetry
- considered plants until 1765
- aggregation of cells built around water canal system
Feeding: filter feeding with intracellular digestion
- water and food particles enter through pores and pass into open center cavity
- flagella move the water in central cavity
- specialized cells facing inside of this avity take up the food
- no true tissues, no gut, no nervous system or circulatory
Diploblasts
characteristics and examples of animals
- Radial symmetry, endoderm/ectoderm
Ctenophores (comb jellies)
Cnidarians (jelyfish, sea anemone, corals)
Cnidarians
Jellyfish, sea anenome, corals
- radial symmetry, diploblast
- mouth connected to gastrovascular cavity
- only one opening (mouth and anus), NO complete gut
- cavity functions in digestion, circulation, gas exchange, hydrostatic skeleton
- specialized musle-like fibers (from ectoderm) whose contractions allow movement
- simple nerve nets to integrate body activities
- specialized carnivores (toxins in tentacles ot capture large prey)
- polyp and medusa life stage
Eumetazoans
“True tissue”
Everything but sponges
Ctenophores
COMB JELLIES
- radial symmetry, diploblast
- two cell layers separated by mesoglea
- “jelly”
- Complete gut
- food enters through mouth and waste eliminated through anal pores
- gas exchange but not a true circulatory system
- Nerve net
- move via beating comb-like rows of fused cilia
- feed on small plankton
- tentacles have adhesive materials that stick to prey
Triploblasts
Bilaterians
Protostomes - blastopore becomes mouth first
Deuterostomes - blastopore becomes anus first
Cnidarian Life cycle
movement, position of mouth, reproduction
- Polyp Stage
- Sessile (don’t move)
- Mouth faces up
- Produce medusa by asexual budding - Medusa Stage
- free-swimming
- floats with mouth and tentacles facing down
- reproduce sexually
Corals
Cnidarians
- diploblasts, radial symmetry, complete gut
- polyps secrete a matrix of organic molecules on which they deposit calcium carbonate, which forms a skeleton
- living polyps form a layer on top of a growing mass of skeletal remains. forms coral reefs and islands
- grow in nutrient poor tropical waters (light is clear so light shines through)
- photosynthetic dinoflagellates live endosymbiotically in their cells
- warming leads to loss of endosymbionts/coral bleaching
- conditions favor algae growth over coral growth
Timeline of Mass Extinctions and causes
- 444 mya - Lower sea levels and glaciation
- 251 mya - The “Great dying, Oxygen levels
- 65.5 mya - Yucatan meteorite (Extraterrestrial event –> climate, oxygen, etc)
Ctenophores vs Cnidarians
Ctenophores (comb jellies)
- Complete gut
Cnidarians (jellyfish, corals, anemones)
- incomplete gut
BOTH:
- diploblasts
- radial symmetry
What makes prokarya and archaea similar?
- DNA is not found in a nucleus and is usually circular
- no membrane bound organelles including nucleus
- divide by binary fission instead of mitosis
Major Eras and Periods of Earth
- Precambrian
- Paleozoic
- Cambrian
- Ordovician
- Silurian
- Devonian
- Carboniferous
- Permian
- Mesozoic
- Triassic
- Jurassic
- Cretaceous
- Cenozoic
- Quaternary
- Tertiary
“PPMC - please pass my cup”
Paleozoic - Main Ideas
3 mass extinction
- Development of SEA creatures
- MASS EXT: sea levels dropped by 50 m
- vascular plants
- MASS EXT: 75% of marine species extinct- 2 meteorites
- animals appear on land, giant insects
- MASS EXT: 96% of species on earth - oxygen levels, “Great Dying”
Mesozoic - Main Ideas
- conifers develop
- frogs
- dinosaurs
- flowering plants
- radiation of plants and animals on land and sea
- MASS EXT: most dinosaurs - meteorite
Cenozoic - Main Ideas
Tertiaty
- flowering plants dominate
- grasslands spread, climate cools
Quaternary
- 4 ice ages
- homo sapiens
