Chapter 2 Flashcards
producers
of an ecosystem provide food for the other organisms present
producers include plants, and other photosynthetic organisms
take co2 and change to sugar
consumers
within an ecosystem eat plants and other animals
require organic material as meal
decomposers
breakdown wastes and dead organisms recycling nutrients so that they can be used for biosynthesis
ex) fungi, bacteria, small animals present in soil
break down dead, organic material
organims within an ecosystem interact with
both the living and the non-living components of their environment
there are two ways in which ecosystems can be characterized
- recyling of chemical nutrients: the basic chemicals needed for life, (carbon, nitrogen, oxygen) flow from air an soil to plants, animals, and decomposers and the back to the air and soil
- energy flow: energy is constantly gained and lost from an ecosystem
energy enters an ecosystem when light from the sun is absorbed by plants and other photosynthetic organisms
energy exits an ecosystem as heat
cells
cells are both structural and functional units of life
the cell is the basic unit of life and is therefore the lowest structural level capable of preforming all activities necessary for life
the structure and function of a cell wall are well correlated to one another: an emergent property
cellular functions include
- responding to enviornmental changes
-the ability to take in and use energy - regulating their own internal enviornment
-ability to produce and maintain its complex organization - the ability to give rise to new cells
: the basis of reproduction, growth, and repair of multicellular organisms
two main cell types
- prokarote
2. eukarotye
prokaryote cells
-unicelllar
-smaller than eurkaryotic cells
-less complex than eukaryotes
-non membrane bound nucleus
-no memebrane bound organelles
ex) bacteria
10 min to split
eukarote cells
-unicellular or multi cellular
-larger than prokaryotic cells
-more complex than prokarotes
-membrane bound nucleus
-membrane bound organelles
ex) animal cell
10 hours to split
all organisms share some common features which include
genetic material present as DNA
cells as the simplest unit of the organism
DNA is organized into functional units called ___?and the DNA itself is made of individual units called ___?
genes and nucleotides ther are four nucelotides that make up DNA adenine A thymine T cytosine C guanine G
other features common among all life forms include
complex organization: highly ordered structure
a highly regulated internal environment: constant internal environment despite constantly changing external environments
the ability to grow and develop: genes which are inherited control growth and development
the ability to take in and utilize energy: the energy is used to preform all the necessary life functions
the ability to respond to enviornmental changes and stimuli
the ability to reproduce ones own kind
evolution of adaptation: this occurs over many generations, individual with traits best suited to their enviornment will pass them on to their offspring
there are how many species that are known and named
1.8 million
estimates of the true number of species range from 10 million to 400 million
taxonomy
is the branch of biology that names and classifies these species into groups based on similarity
all life can be organized into three domains
1) domain bacteria (prokaryotes)
2) domain archaea ( prokaryotes)
3) domain eukarya
kingdoms of the domain eukarya
there are four kingdoms within the domain eukarya:
1) kingdom protista: single celled protozoans and algae (singler and multi cellular)
2) kingdom plantae: photosynthesis plants
3) kingdoms fungi: molds, yeasts, and mushrooms
4) kingdom animalia: animals: vertebrates and invertabrates
charles darwin
- species present today arose from ancestral species
- he was able to explain both the unity of life (decent from a common ancestor) and the diversity of life (modifications as species diverged from common ancestor)
- darwin proposed that the mechanism of evolution was natural selection
- based on the observations of unequal reproduction success
- the environment selects fro certain traits
- this results in the accumulation of favorable traits in a population over time
natural selection
individuals within a population have varied traits which are inheritable
not all offspring will survive and only those that do will be given the chance to reproduce
the individuals with the most desirable traits will be able to survive and reproduce and the resulting population will therefore be enriched with organisms that have these traits
evolutionary adaptation
all organisms have specific adaptations that have evolved as a direct result of natural selection
antimicrobial resistance has also developed as a result of natural selection
-a resistant species devlelop in a short time period
adaptations
inherited traits that function to enhance an organisms ability to survive in a specific environment
pre-darwin evolutionary theories
greek philosophers initially beilieved that life likely changed gradually
aristotle view was that species were perfect and permanent
during this time it was also believed that earth was only 6,000 years old and that species were static in their form
during the mid 1700’s fossils were studied revealing that there were previous life forms that differed from those seen today
jean baptise lamarck hypothesized in the early 1800’s that life forms evolve
his theory was that this evolution took place according to use and non-use of various body parts which is erroneous
lamarks theory explained the long neck of the giraffe was the result of persistent stretching in order for the giraffe to reach higher trees
all about charles darwin
during the mid- 1800’s darwin set sial around the world as captain of the HMA beagle
he collected plants, animals, and fossils from the shores of south america
-he noted adaptations of organisms from very different environment such as the Brazilian jungle and the Argentinian grassland
-he noted that the individual islands of the galapagos island has species that were different than those of other islands
he also discovered that these islands has species similar to but different than those species found on the nearby mainland
-these observations led him to doubt the pre-exsisting theory that earth and all of its organisms has been created only a few thousand years earlier
-darwin documented his orservations but delayed publishing his theory of evolution because he knew that it would not be widely accepted
in the mid 1850’s alfrwed wallce put forth a similar theory of evolution as darwins
darwin published a book highlighting his theory in 1858 called “on the origin of species by means of natural selection
-evidence that present say species arose from ancestors
-as the descendants of a remote ancestor moved into various different environments they developed diverse adaptions that made them equipped to survive
-he proposed that the mechanisms of this evolution is natural selection
artifical selection
the modification of species by selecting and breeding those individual that possess desired traits
natural selection
a similar process to artificial selection but occurring in nature
this theory was based on two key observations
1. members of a population vary in their traits and most traits are inherited from parents to offspring
2. all species are capable of producing more offspring than the enviornment can support
he then infered that:
1. indivduals whose inherited traits provide them a higher probability of surviving and reproducing ina given environement tend to leave more offspring behind than other indivduals
2. this unequal production of offspring will cause favourbale traits to acumlate in an environment
natural selection
pesticise resistance as an example of natural selection
- bugs with the red gene are resistant to pesticides
- bugs with the green gene are susceptible to pesticides
- application of the pesticide leads to a population enriched with resistant buys
- future applications of the pesticide will be less effective
more charles
darwin suggested that if artificial selection can bring about so much change over such a small time period then natural selection has the capacity to considerably modify species over thousands of generations
- therefore many traits that allow an organism to adapt to a particular environment will accumulate over time
- if the environment changes or the organism moves tp a new environment than natural selection will select for new adaptions that make the organism more equipped to survive
fossils provide
comparrisons between past organisms and present organisms
the study of fossils provide strong evidence for evolution
fossils are usually only replicas of an organism
when the organism decays it forms a mold which is then filled with minerals dissolved in water
different types of fossils
- the fossilized skull of homo erectus
- cast fossils
- trace fossils
- fossilized organic matter
- an insect buried in a tree resin 35 million years ago
- ice also preserves whole organism
the fossilized skull of homo erectus
hard parts of the organism containing minerals such as bone may remain as fossils, while the other substances of the dead organisms usually decay rapidly
cast fossils
replicas of the organism formed when the organism decays and water and dissolved minerals fill its place
ex) ammonite casts (shelled organisms) 375 million years old
trace fossils
there are footprints, burrows, and others behavioural remnants
150 million year old dinosaur track in colorado
fossilized organic matter
ex) 40 million year old leaf
an insect buried in a tree resin 35 million years
the resin hardened into amber preserving the insect by protecting it form decomposition by bacteria and fungi
ice also preserves whole organisms
discovered in 1991, ice man was dead in the ice for 5000 years
the fossil record
this is the sequence in which fossils appear in the layers of sedimentary rock
deposits pile up over millions of years wirth the older sediments becoming buried below into rock
strata or layers are formed within the rock with younger strata atop older strata
the realitive age of a fossil can be determined by the layer in which it was found
the oldest known fossils date back 3.5 billion years and all are those of prokaryokes
-single celled eukaryotes arose 1.0 billion years later
-another 1.0 billion years passed before mutli-celled eukatotes were formed
fossils trace the evolution of whales into four-legged land mammals
other evidence for evolution
biogeography
comparative anatomy
compartive embryology
molecular biology
biogeography
- the geographical distrubition of species also suggests that organisms evolve from a common ancestor
- the island forms of certain species found on the mainland than those found on nearby island
- darwin noted that animals on the galapogoes islands are more closely resembled animals on the south american mainland than animals on similar but distant islands
comparative anatomy
comparing body structures in different species reveals homology suggesting a common ancestor
homology
the similarity in characteristics that result from a common ancestor
homologous structure
structure that are functionally different but have similar structures because of a common ancestor
ex) human, cat, whale, bat -arm, leg, fin, wing
analogous structure
structure that are functionally the same but a different evolutionary origin
ex) bats, blue birds, butterflys - wings
comparative embryology
organisms go through similar embryonic stages
comparison of the structures that appear during the development of different organisms suggest common ancestry
ex) many vertebrae species share common embryonic structures
molecular biology
individuals that arose from a common ancestor have greater similarity in their DNA and protein than do unrelated individuals
species that are closely related to one another have much higher percentage of identical amino acid sequences
a comparison of amino acid sequences serves as a evaluation of the relatedness of the two species
evolutionary trees
each branch point represents the common ancestor of the lineages beginning there or to the right of it
a hatch mark represents a homolgous characteristic shared by all groups to the right of the mark
homologus structures both anatomical and molecular can be used to determine the branching sequence of the tree
population
a group of individuals of the same species living in the same place at the same time
population genetics
the study of how populations change genetically over time
scientists that study evolution as the population level focus on the gene pool which is the total collection of genes in a population at any given time
-for most genes there are at least two alleles in the gene pool
-ex) an allele for a bug that is resistant to pesticides and an allele for a bug that is not resistant to pesticides
-when the pesticides are applied the allele frequency of the resistant gene will increase and the allele frequency of the susceptible gene will decrease
microevolution
microevolution is the gradual change in the gene pool of a population over time
- when allele frequencies are changing in a population over a number of generations evolution occurs on its smallest scale
ex) hair color lighter everyday just by slightest shade - eventually blonde
- day to day unnoticeable, over time big change
generation of genetic variation
new alleles can be created by mutation
mutation is a change in the nucleotide sequence of DNA
sexual recombination: this generates variation by shuffling alleles during meiosis
factors that contribute to evolution
- natural selection
- genetic drift
- gene flow
natural selection
this leads to differential reproductive success in a population
this can alter frequencies in a population
genetic drift
this is a change in the gene pool of a population due to chance
natural disaster, mass extinction, colonization of new areas
can alter allele frequencies in a population
can cause the bottle neck effect or the founder effect
gene flow
the movement (immigration or emigration) of individuals between populations
this can alter frequencies in a population
gain or loss of alleles
bottle neck effect
floods, fires and earthquakes can kill large numbers of people leaving behind a small surviving population that is unlikely to have the same genetic makeup as the original population
founder effect
the founder effect results when a few individuals colonize a new environment such as an isolated island
the smaller this new group is the less likely the genetic makeup of the new population will resemble that of the larger population that they left
the founder effect refers to the differences between the gene pool of the new population and the gene pool of the original population
endangered species
often have reduced variation
-the bottle neck effect
-there is a loss of genetic variability due to over hunting and habitat loss
-a high level of inbreeding occurs because the population is so small
-this may reduce the capacity of endangered species to survive as humans continue to alter the environment
ex) decreasing cheetah population
decreasing genetic diversity
leads to increased inbreeding
a high amount of genetic uniformity
natural selection alters variation
- stabilizing selection
- directional selection
- disruptive selection
stabilizing selection
this favors intermediate phenotypes
low black, high grey, low white
directional selection
this acts against individuals at one of the phenotypes extremes
low black, low grey, high white or
high black, low grey, low grey
disruptive selection
this favours individuals at both extremes of the phenotypic range
high black, low grey, high white
sexual selection
sexual selection occurs when individuals with certain characteristics are more likely to obtain mates
- a form of natural selection
- leads to the evolution of secondary sex characteristics
- these characteristics may provide individuals with a mating advantage
four reasons that natural selection produces less than perfect organisms
- selection can only act on existing variations
- evolution is limited by historical constrains
- adaptations are often comprises
- chance, natural selection and the environment all interact
selection can only act on existing variations
natural selection favors only the fittest variations from those which are available
these may not be the ideal traits
new and advantagous alleles cannot arise on demandd
ex) basket ball tryouts of all short people, you cannot just get tall people
evolution is limited by historical constraints
evolution operates on the traits that an organism already has
it does not produce new structures
it modifies existing structures to adapt them to new situations
ex) movement of land animals to water
adaptations are often comprises
each organism must be able to do many different things
ex) ducks, must be able to swim and fly
this is necessity makes their webbed feet less than perfect for walking on land
chance, natural selection and the environment all interact
chance affects the genetic structure of a population to a large extent
not all alleles fixed by genetic drift in a gene pool of a small population are better suited to the environment than the alleles which are lost
