ch. 25 the history of life on earthstaff.katyisd.org/sites/thsbiologyapgt/documents/unit...

AP Biology 2012

Ch. 25 The History of Life on Earth

“We are like butterflies who

flutter for a day and think it

is forever.” ― Carl Sagan

http://www.goodreads.com/author/show/10538.Carl_Sagan

AP Biology

Bacteria Archae- bacteria

Animalia Fungi Protista Plantae

4500

4000

3500

3000

2500

2000

500

1500

0

1000

Formation of earth

Molten-hot surface of earth becomes cooler

Oldest definite fossils of prokaryotes

Appearance of oxygen in atmosphere

Oldest definite fossils of eukaryotes

First multicellular organisms

Appearance of animals and land plants

Colonization of land by animals Paleozoic

Mesozoic

Cenozoic

Millio

ns

of

ye

ars

ag

o

AR

CH

EA

N

PR

EC

AM

BR

IAN

PR

OT

ER

OZ

OIC

The evolutionary tree of life can be documented with evidence.

The Origin of Life on Earth is another story…

AP Biology

What is Life?

First we have to define LIFE…

organized as cells

respond to stimuli

regulate internal processes homeostasis

use energy to grow metabolism

develop change & mature

within lifetime

reproduce heredity

DNA / RNA

adaptation & evolution

AP Biology

The Origin of Life is Hypothesis Extraterrestrial Origin

Was the original source of organic (carbon) materials comets & meteorites striking early Earth?

testable

Spontaneous Abiotic Origin

Did life evolve spontaneously from inorganic molecules?

testable

AP Biology

Conditions on early Earth

Reducing atmosphere

water vapor (H2O), CO2, N2, NOx, H2, NH3,

CH4, H2S

lots of available H & its electron

no free oxygen!

Energy source

lightning, UV radiation,

volcanic

low O2 =

organic molecules

do not breakdown

as quickly

What’s missing from that

atmosphere?

AP Biology

Water vapor

Condensed liquid with complex, organic molecules

Condenser

Mixture of gases ("primitive atmosphere")

Heated water ("ocean")

Electrodes discharge sparks

(lightning simulation)

Water

Origin of Organic Molecules

Abiotic synthesis

1920 Oparin & Haldane propose reducing atmosphere hypothesis

1953 Miller & Urey test hypothesis formed organic

compounds amino acids

adenine

CH4

NH3 H2

AP Biology

Stanley Miller

University of Chicago

produced

-amino acids

-hydrocarbons

-nitrogen bases

-other organics

It’s ALIVE!

AP Biology

Bubbles… Tiny bubbles…

Origin of Cells (Protobionts) Bubbles separate inside from outside

metabolism & reproduction

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Origin of Genetics

RNA is likely first genetic material

multi-functional

codes information self-replicating molecule

makes inheritance possible

natural selection & evolution

enzyme functions ribozymes

replication

regulatory molecule

transport molecule tRNA & mRNA

Dawn of natural selection

AP Biology

Key Events in Origin of Life

Key events in

evolutionary

history of life on

Earth

life originated

3.5–4.0 bya

AP Biology

Prokaryotes

Prokaryotes dominated life

on Earth from 3.5–2.0 bya

3.5 billion year old

fossil of bacteria modern bacteria

chains of one-celled cyanobacteria

AP Biology

Stromatolites Fossilized mats of prokaryotes resemble modern microbial colonies

Lynn Margulis

AP Biology

Oxygen atmosphere Oxygen begins to accumulate 2.7 bya

reducing oxidizing atmosphere evidence in banded iron in rocks = rusting

makes aerobic respiration possible

photosynthetic bacteria (blue-green algae)

AP Biology

First Eukaryotes

Development of internal membranes create internal micro-environments

advantage: specialization = increase efficiency natural selection!

infolding of the plasma membrane

DNA

cell wall

plasma membrane

Prokaryotic cell

Prokaryotic ancestor of eukaryotic

cells

Eukaryotic cell

endoplasmic reticulum (ER)

nuclear envelope

nucleus

plasma membrane

~2 bya

AP Biology

Endosymbiosis

Ancestral eukaryotic cell

Eukaryotic cell with mitochondrion

internal membrane

system aerobic bacterium mitochondrion

Endosymbiosis

Evolution of eukaryotes origin of mitochondria

engulfed aerobic bacteria, but did not digest them

mutually beneficial relationship

natural selection!

AP Biology

mitochondrion

chloroplast

Eukaryotic cell with

chloroplast & mitochondrion

Endosymbiosis

photosynthetic

bacterium

Endosymbiosis

Evolution of eukaryotes origin of chloroplasts

engulfed photosynthetic bacteria, but did not digest them

mutually beneficial relationship natural selection!

Eukaryotic cell with

mitochondrion

AP Biology

Variations in Cell Interior

aerobic bacterium

mitochondria

cyanobacterium

(photosythetic) bacterium

chloroplast

AP Biology

Evidence

structural mitochondria & chloroplasts

resemble bacterial structure

genetic mitochondria & chloroplasts

have their own circular DNA, like bacteria

functional mitochondria & chloroplasts

move freely within the cell

mitochondria & chloroplasts reproduce independently from the cell

Theory of Endosymbiosis

Lynn Margulis

AP Biology

The chimera of Greek

mythology was part goat,

part lion, and part serpent.

The eukaryotic cell is a

“chimera” of prokaryotic

parts:

mitochondria from one bacteria

plastids from another

nuclear genome from the host cell

The eukaryotic cell is a chimera

of prokaryotic ancestors

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

AP Biology

The first great adaptive radiation, the

metabolic diversification of the prokaryotes,

set the stage for the second.

The second wave of diversification was

greater structural diversity-The Protists.

The third wave of diversification followed the

origin of multicellular bodies in several

eukaryotic lineages- Plants, Fungi, Animals.

The origin of eukaryotes catalyzed a

great waves of diversification


AP Biology

“Evo-devo”: Developmental genes

play a major role in evolution

Genes that program development by controlling the rate, timing, and spatial pattern of changes

Allometric growth

AP Biology

Change the relative rates of growth even

slightly, and you can change the adult

from substantially.

Neoteny- retention of

juvenile features into

adulthood. Note how

in humans we have

kept juvenile facial

features by not

developing heavy

eyebrow ridges and

a snouty upper jaw


Fig. 24.19b

AP Biology

Evolutionary Developmental Biology

Major questions in Evo-Devo How do HOX genes provide positional

information?

How are Gene pathways directed?

How can developments evolve?

AP Biology

Hox Genes Hox (homeobox) genes

control the morphology

of segments in animals.

Discovered in the

70s and 80s

Homeotic selector

genes - control

patterning of

body structures

AP Biology

Mutations in Hox genes

AP Biology

The Homeobox A highly conserved amino acid sequence,

shared among Hox genes, that binds DNA

Thus, Hox genes regulate the transcription

of other genes – typically, genes that are

part of gene cascades involved in

development.

Transcription factor: a protein that, by

interacting with a regulatory DNA sequence,

affects the transcription of the associated

gene

AP Biology

Expression

Occurs in an

anterior-posterior

pattern

Segment-specific

expression in mouse

hindbrain

AP Biology

Anterior-posterior

patterns of HOX

expression: highly

conserved.

AP Biology

How is position-specific expression achieved?

Segmentation genes

establish early embryonic

spatial patterns of

transcription factors.

These transcription factors

drive the spatial pattern of

HOX gene expression.

HOX genes then trigger cascades of developmental

gene pathways (via transcription factors for genes that

influence the expression of yet other genes).

AP Biology

Ancestral Pathway

New Regulatory

Genes

Conserved

Regulatory

Genes

Changed Pattern of

Regulatory Gene

Expression

New Domains

of Expression

Conserved Pattern

Regulatory Gene

Expression

New

Promoter

Affected by

Transcription

Factor

Modification of

Expression within

Conserved

Domain

Change in

Sequence

of Target

Gene

AP Biology

New HOX genes for new segmental morphologies?

Ed Lewis’ model 1978

AP Biology

Hox genes act by regulating multiple target genes

Ubx- regulated expression of

leg development

Less Ubx expression in the

posterior segments of

Drosophila results in

suppression of leg formation.

AP Biology

HOX genes: Regulate multiple target genes

Have distinct sets of downstream targets

Target genes change during evolution,

Changes HOX gene functions

HOX genes are highly conserved

We still know very little about the

downstream targets of the HOX genes

The more things change, the more they stay the same

AP Biology

Evolution is not goal-oriented

An evolutionary trend does not mean that evolution is goal-oriented.

Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well Remember that for humans as well!

Evolution is not the

survival of the fittest.

Rather it is the

survival of the just

good enough.

AP Biology

Cambrian explosion Diversification of Animals

within 10–20 million years most of the major phyla of animals

appear in fossil record

Evolution of hard shells…indicates a new mode of defense

against predators?

543 mya

AP Biology

AP Biology

Plant Diversity

Bryophytes

non-vascular

land plants

Pteridophytes

seedless

vascular plants

Gymnosperm

pollen &

“naked” seeds

Angiosperm

flowers & fruit

pollen & seeds

vascular system = water conduction

mosses ferns

conifers flowering plants

colonization of land

Tracheophytes

xylem cells = tracheids Ancestral Protist

flowers

AP Biology

Animal vs. Plant life cycle

diploid multicellular

individual 2n

diploid multicellular sporophyte

2n

haploid multicellular gametophyte

1n

haploid unicellular gametes

1n

gametes 1n

Animal Plant

alternation of generations

meiosis

fertilization

mitosis

mitosis mitosis

fertilization

mitosis

no multicellular haploid

meiosis

spores 1n zygote 2n

zygote 2n

AP Biology

First land plants-Nonvascular– 450 MYA

Bryophytes: mosses & liverworts

non-vascular

no water transport system

no true roots

swimming sperm

flagellated sperm

lifecycle dominated by

haploid gametophyte stage

fuzzy moss plant you are

familiar with is haploid

spores for reproduction

haploid cells which sprout

to form gametophyte

diploid haploid

Where must mosses live?

AP Biology

First vascular plants – 400 MYA

Pteridophytes: Ferns

vascular water transport system

xylem, phloem, roots, leaves

swimming sperm flagellated sperm

life cycle dominated by sporophyte stage leafy fern plant you are

familiar with is diploid

fragile independent gametophyte (prothallus)

spores for reproduction haploid cells which sprout

to form gametophyte

diploid

Where must ferns live?

haploid

AP Biology

First seed plants – 350 MYA Gymnosperm: conifers

Vascular – xylem and phloem

heterospory male vs. female gametophytes

seeds naked seeds (no fruit)

pollen contain male gametophyte

spread by wind

life cycle dominated by sporophyte stage coniferous trees you are familiar with are diploid

reduced (microscopic) gametophyte

reduction of gametophyte protects delicate egg & embryo in protective sporophyte

protected from drought & UV radiation

AP Biology

First flowering plants – 130 MYA Angiosperm: flowering plants

Vascular – xylem and phloem

heterospory male vs. female gametophytes

flower specialized structure for sexual reproduction

seeds within fruit

Pollen - spread by wind or animals

life cycle dominated by sporophyte stage trees & bushes you are familiar

with are diploid

reduced (microscopic) gametophyte

AP Biology

Co-evolution: flowers & pollinators

The mirror ophrys (Ophrys

speculum) flower resembles

that of the female wasp Colpa

aurea. Males of the species

pick up pollen during their

attempts at copulation.

How a bee sees a flower…insects see

UV light = a bulls-eye to the nectar

AP Biology

Porifera

Cnidaria

Platyhelminthes

sponges jellyfish flatworms roundworms

Nematoda

Mollusca Arthropoda Chordata

Annelida Echinodermata

mollusks

multicellularity

Ancestral Protist

tissues

bilateral symmetry

body cavity

segmentation

Animal Evolution

coelom

starfish vertebrates

endoskeleton

segmented worms

insects spiders

backbone

specialization & body complexity

specialized structure & function,

muscle & nerve tissue

distinct body plan; cephalization

body complexity

digestive & repro sys

digestive sys

body size

redundancy,

specialization, mobility

body & brain

size, mobility

radial

bilateral

AP Biology

Body Cavity ectoderm

ectoderm

mesoderm

endoderm

ectoderm

mesoderm

endoderm

mesoderm

endoderm

acoelomate

pseudocoelomate

coelomate

coelom cavity

pseudocoel

Space for organ system development

increase digestive & reproductive systems

increase food capacity & digestion

increase gamete production

Coelem

mesoderm & endoderm interact during development

allows complex structures to develop in digestive system

ex. stomach

protostome vs. deuterostome

AP Biology

Vertebrates

fish, amphibians, reptiles, birds, mammals

internal bony skeleton

backbone encasing

spinal column

skull-encased brain

deuterostome

postanal tail notochord

hollow dorsal nerve cord

pharyngeal pouches

Chordata

becomes brain & spinal cord

becomes vertebrae

becomes gills or Eustachian tube

becomes tail or tailbone

Oh, look… your first

baby picture!

AP Biology

Urochordates, such as the adult sea squirt (right) have larvae with:

•A hollow, dorsal nerve cord •A notochord

•Pharyngeal pouches •post-anal tail

•Think about this: How could

Evo-Devo lead to the evolution of the vertebrates?

Sometimes,

immaturity pays off!

AP Biology

Vertebrates: Fish salmon, trout, sharks

450 mya

Characteristics

body structure

bony & cartilaginous skeleton

jaws & paired appendages (fins)

scales

body function

gills for gas exchange

two-chambered heart;

single loop blood circulation

Ectotherms

gills

body

AP Biology

Evolution of Jaws – about 475 Million years ago. First set of gill

arches were modified into a early set of jaws.

AP Biology

Vertebrates: Fish salmon, trout, sharks

450 mya

Characteristics

reproduction

External fertilization, but three means of delivery…

Oviparous- external development in

aquatic egg outside the body.

Ovoviviparous- retain fertilized eggs in the oviduct.

Viviparous- provide nutrients to the developing

offspring.

buoyancy

Sharks/Rays – use oily liver

Boney Fish – use swim bladder

AP Biology

Transition to Land

Evolution of tetrapods

Tibia

Femur

Fibula

Humerus Shoulder

Radius Ulna

Tibia

Femur Pelvis

Fibula Lobe-finned fish

Humerus

Shoulder

Radius

Ulna

Pelvis

Early amphibian

This reminds me of tadpoles, not

that I’ve ever seen one in Anarctica

AP Biology

lung

buccal cavity

glottis closed

Vertebrates: Amphibian

Characteristics

body structure legs (tetrapods)

moist , porous skin

body function lungs (positive pressure) &

diffusion through skin for gas exchange

three-chambered heart; veins from lungs back to heart

ectotherms

reproduction external fertilization (Oviparous)

external development in aquatic egg

metamorphosis (tadpole to adult)

frogs

salamanders

toads

350 mya

AP Biology

Amphibian Metamorphosis

Transitions from a fish-like creature

to a land-living creature.

•Gills,lateral line, fin,

swim bladder

•Gills- replaced with lungs

•Lateral line disappears

•Fin replaced with legs

•Swim bladder turns

into lungs

AP Biology

Amphibian Circulatory System

Two-chambered heart

as tadpole

Three-chambered heart as adult

Note: oxygenated blood mixes with CO2-carrying blood in the

ventricle-not so efficient, but good enough if you’re ectothermic.

AP Biology

Vertebrates: Reptiles Characteristics

body structure dry skin, scales, armor

body function lungs for gas exchange

thoracic breathing; negative pressure

three-chambered heart

ectotherms

reproduction internal fertilization

external development in amniotic egg

250 mya dinosaurs, turtles

lizards, snakes

alligators, crocodile

embryo leathery shell

chorion

allantois yolk sac

amnion

AP Biology

AP Biology

The amniote clade consists of the mammals, the birds, and

the vertebrates commonly called reptiles, including turtles,

lizards, snakes, and crocodiles.

The evolution of amniotes from an amphibian ancestor

involved many adaptations for terrestrial living including:

the amniotic egg

waterproof skin

increasing use of the rib cage to ventilate the lungs

as skin was no longer useful for respiration.

Evolution of the amniotic egg expanded

the success of vertebrates on land


AP Biology

The amniotic eggs enabled terrestrial vertebrates to

complete their life cycles entirely on land.

Reptile eggs have a leathery shell that retains

water and can be laid in a dry place.

The calcareous shells of bird eggs are inflexible,

while the leathery eggs of many reptiles are

flexible.

Most mammals have dispensed with the shell.

The embryo implants in the wall of the uterus

and obtains its nutrition from the mother.


AP Biology

Inside the shell of the amniotic egg are several

extraembryonic membranes that function in gas exchange,

waste storage, and the transfer of stored nutrients to the

embryo.

These develop from tissues layers that grow out

from the embryo.


Fig. 34.19

AP Biology

Vertebrates: Birds (Aves) Characteristics

body structure feathers & wings

thin, hollow bone; flight skeleton

body function very efficient lungs & air sacs

four-chambered heart

endotherms


external development in amniotic egg

150 mya finches, hawk

ostrich, turkey

trachea

anterior air sacs

lung

posterior air sacs

AP Biology

AP Biology

The most obvious adaptations for flight are wings.

Wings are airfoils that illustrate the same principles of

aerodynamics as airplane wings.

Pressure differences created by differences in air flow over the top (low pressure) and bottom of the convex wing (high pressure) lift the wing and the bird.

Large pectoral (breast) muscles anchored to a keel on the sternum (breastbone) power flapping of the wings.


Fig. 34.26

AP Biology

Vertebrates: Mammals

220 mya / 65 mya mice, ferret

elephants, bats

whales, humans

muscles contract

diaphragm contracts

Characteristics

body structure hair

specialized teeth

body function lungs, diaphragm; negative pressure

four-chambered heart

endotherms


internal development in uterus

nourishment through placenta

birth live young

mammary glands make milk

AP Biology

Feeding adaptations of the jaws and teeth are

other important mammalian traits.

teeth of mammals come in a variety of

shapes and sizes adapted for processing

many kinds of foods.

During the evolution of mammals from

reptiles, two bones formerly in the jaw joint

were incorporated into the mammalian ear

and the jaw joint remodeled.


AP Biology

Specialized teeth:

Herbivores -Sharp incisors

-Flat molars

-No canines

Carnivores -sharp canines

-sharp, shearing molars

AP Biology

Vertebrates: Mammals Sub-groups

monotremes egg-laying mammals

lack placenta & true nipples

duckbilled platypus, echidna

marsupials pouched mammals

offspring feed from nipples in pouch

short-lived placenta

koala, kangaroo, opossum

placental true placenta

nutrient & waste filter

shrews, bats, whales, humans

AP Biology

AP Biology

Diversity of life & periods of mass extinction

Cambrian

explosion

The fossil

record

records five

to seven

severe mass

extinctions.

AP Biology

Permian mass extinction (250 million years ago)

claimed about 90% of all marine species.

occurred in less than five million years.

thought to have been caused by the effects of a huge

mantle plume that reached the surface in central Siberia,

generating thousands of square miles of lava several

thousand feet thick.


AP Biology Copyright © 2002 Pearson Education, Inc., publishing as Benjamin

Cummings

The Cretaceous mass extinction (65 million years ago) -

half of the marine species and many families of terrestrial plants and animals, including nearly all the dinosaur lineages.

Hypotheses for this extinction include:

The climate became cooler, and shallow seas (Sundance Sea) receded from continental lowlands.

Large volcanic eruptions in India (Deccan Traps) may have contributed to global cooling by releasing material into the atmosphere.

And….

AP Biology Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Comet or Asteroid Impact-

Walter and Luis Alvarez – discovered a

thin layer of clay enriched with iridium,

an element rare on Earth but common in

meteorites and other extraterrestrial

debris in deposits of the K/T boundary.

Proposed an asteroid impact that

produced a great cloud that would have

blocked sunlight and disturbed the

climate for several months.

Recent research has focused on the

110 km wide Chicxulub crater, a 65-

million-year-old scar located beneath

sediments on the Yucatan coast of

Mexico.

AP Biology

Diversification of the

surviving groups

result as producer

communities recover

and new niches open

up. Organisms then

“rapidly” evolve to

take advantage of

those niches, along

with their prey,

predators, parasites,

etc….

Mass extinctions are followed by

Adaptive Radiations.


AP Biology

Early mammal evolution

125 mya mammals

began to radiate

out & fill niches.

However, at no time before the

end of the Cretaceous did any

mammal weigh more than 30 pounds.

AP Biology 2008-2009

Any Questions??

Is there life elsewhere?

Does it look like life on Earth?

ch. 25 the history of life on earthstaff.katyisd.org/sites/thsbiologyapgt/documents/unit...

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