VI - Evolution & Biodiversity: Origins, Niches, & Adaptation Flashcards
biodiversity
(=biological diversity) variety of different species, genes, or ecosystems
types main types of life
Prokaryotes
Eukaryotes
Prokaryotes
organisms (bacteria) whose cells do not have a distinct nucleus or other internal parts enclosed in membranes.
Eukaryotes
organisms whose cells have a distinct nucleus and various internal parts enclosed in membranes.
Six kingdoms
Archaebacteria Eubacteria Protista Plantae Fungi Animalia
Prokaryotes means
“before nucleus”
Eukaryotes means
“true nucleus”
archaebacteria & eubacteria
single–celled, microscopic prokaryotic organisms, in particular bacteria & cyanobacteria.
protista/protist
mostly single–celled eukaryotic organisms
Protist examples
diatoms, dinoflagellates, amoebas, golden– brown & yellow–green algae, & protozoans.
fungi
mostly many–celled (some single–celled) eukaryotic organisms
fungi examples
mushrooms, molds, mildews, & yeasts.
plantae (plants)
mostly many–celled eukaryotic organisms
plantae (plants) examples
red, brown, & green algae, mosses, ferns, conifers, & flowering plants
animalia (animals)
many–celled eukaryotic organisms
animalia (animals) examples
sponges, jellyfish, sponges, mollusks, worms, arthropods, fish, amphibians, reptiles, birds, & mammals
Animalia can be split mostly into two main categories …
Invertebrates
Vertebrates
species
a distinct kind of organism; groups of organisms that resemble each other, &, in cases of sexually reproducing organisms, can potentially interbreed
Each species is assigned a
Scientific name
Scientific name
Derived from Latin
Consisting of two parts (genus + specific epithet)
Always written in italics or underlined.
Scientific name examples
Ursus horribilis is the grizzly bear
Taraxacum officinale is the dandelion
each species is classified in a
hierarchical taxonomic classification
hierarchical taxonomic
classification tiers
Kingdom Phylum Class Order Family Genus Species
Classification of humans
Kingdom: Animalia Phylum: Chordata Sub-phylum: Vertebrata Class: Mammalia Order: Primates Family: Hominidae Genus: spaiens Species: sapiens sapiens
What two main evolution lead to life?
Chemical evolution
Biological evolution
Chemical evolution took place over the course of…
1 billion years
Biological evolution took place over the course of …
3.7 billion years
Chemical evolution
Formation of crust & atmosphere
Small organic molecules in seas
Large organic molecules in seas
First protocells in seas
Biological evolution
Single-cell prokaryotes in sea
Single-cell eukaryotes in seas
Variety of multicellular organisms first in sea, then on land
Why is Earth “just right” for life?
distance from sun size rotation orbit around sun atmospheric evolution
distance from sun
leads to a temperature range favorable to life (between freezing & boiling point of water) energy flow from sun sufficient to drive weather & supply energy for life
size
enough gravitational mass to hold its atmosphere of light molecules (N2, O2, CO2, and H2O) and to keep its core molten
rotation
leads to daily patterns (night & day)
orbit around sun
leads to seasonal patterns
atmospheric evolution
accumulation of O2 in lower atmosphere formation of ozone shield to screen harmful ultraviolet (UV) radiation
evolution
change in a population’s genetic makeup through successive generations.
Microevolution
change in gene frequency within a population short–term evolutionary changes
Macroevolution
the formation of new species from ancestral species
long–term evolutionary changes
four processes drive microevolution
gene flow
genetic drift
mutation
natural selection
gene flow
the movement of genes between populations
genetic drift
change in genetic composition that results by chance, especially in small populations
mutation
random changes in the structure of DNA molecules that serve as the ultimate source of genetic
variation
natural selection
the process by which some individuals of a population have genetically based characteristics that cause them to survive & produce more offspring than other individuals
three conditions required for natural selection
variability
heritability
differential reproduction
variability
there must be natural variability for a trait within a population
heritability
the trait must be inheritable, meaning that it has a genetic basis such that it can be passed from
generation to generation
differential reproduction
the trait must enable individuals with the trait to leave more offspring than other members of the population
adaptation
a heritable trait that enables organisms to better survive & reproduce within a given set of environmental
conditions
peppered moth variability
two color forms, one dark & one light light form originally more common because it blended in with lichens on trees & was not easily eaten by birds
peppered moth heritability
color form was genetically based
peppered moth differential reproduction
during the industrial revolution of the mid–1800s in England soot coated trees dark form became more common because light individuals became easier for birds to find & dark form blended in.
The peppered moth is a class example of
microevolution
Directional selection
favors individuals with traits that are at one end of a distribution
Directional selection example
Peppered moth
Stabilizing selection
eliminates individuals at both in of the spectrum of variation the average remains the same
Diversifying selection
eliminates average individuals, but favors individuals at either extreme of the spectrum of variation
coevolution
involves interactions between two species that result in ongoing evolutionary changes in each of the species.
coevolution in flowering plants & their pollinators
flowers attract pollinators & provide “reward” for food in the form of nectar or pollen
pollinators perform “service” of moving
pollen between flowers
coevolution in plants with defenses
plants with defenses against herbivores (thorns, camouflage, toxins) & the herbivores’ ability to deal with plants’ defenses
niche
the functional role of a species in an ecosystem
niche can include
• conditions (physical & chemical)
• resources (such as nutrients or food)
• interactions with living (biotic) & nonliving (abiotic)
components of ecosystem
• role in flow of energy cycling of matter
Niche and habitat are …
Not the same
Habitat
actual location where an organism lives
Niche can be compared to the…
Occupation of an organism
Habitat can be compared to the …
Address of an organism
adaptation
any genetically controlled trait that helps an organism survive & reproduce in a given set of environmental conditions
Relationship between ecological niche & adaptation
species with similar niches tend to evolve similar sets of traits
Convergence
resemblance of different species with similar niches
Examples of convergence
- desert shrubs of different parts of world have deep roots, small leaves, & high tolerance to hot, dry conditions.
- herbivores of different parts of world have traits to forage & digest plant material, escape predators, & migrate or become dormant when food is scarce.
Macroevolution involves three processes:
- evolutionary change of lineage through time
- speciation: formation of new species
- extinction: loss of species
new species typically evolve by two steps:
Geographic isolation
Reproductive isolation
geographic isolation
separation into distinct populations with different evolutionary pressures
reproductive isolation
evolutionary changes in each population that prevent interbreeding when populations come into contact.
Geographic
isolation can
lead to
reproductive
isolation
divergence
speciation
Speciation in early fox
Split into northern and southern population, each adapting to own env’tal pressures
Northern -> Arctic
Southern -> Gray
Fossil record shows evidence of extinction as a …
natural process
Background extinction
loss of species at a relatively low rate, often due to changes in local conditions
Mass extinction
abrupt increases in extinction rates above the background level.
How many great mass extinction have occurred during the past 500 million years?
5
mass extinctions believed to result from
global climate changes
recent extinctions caused by humans at
exceptionally high rates
Continental drift
Slow movement of continents
Major role in speciation & extinction
Adaptive Radiation
splitting of a lineage to form many species with different ecological niches
Adaptive radiation of mammals began about
65 million years ago
What is the appropriate time frame for thinking about
environmental problems?
• humans have existed on a tiny fraction of geological or
evolutionary time scales;
• earth’s biodiversity has taken millions of years to
evolve & is not replaceable in human time scale;
• extinction is natural process, but human–induced
extinction is occurring at unprecedented rates.
Can we heal the earth?
• requires lots of time & money;
• better to prevent environmental degradation & loss of
biodiversity.
