SCILIVSY 12 Chapter 3: SLS12- Chapter 3
19 Jun 2018
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The$determinant$for$which$species'$characteristics$survive$and$
others$become$extinct
§
Woodpecker's$beak$allows$it$to$gather$insects
□
A$parasite's$structure$allows$it$to$attach$to$and$feed$off$
another$organism
□
Bettles'$ability$to$dive$into$water$an$gather$food
□
Great$variations$in$species$have$allowed$plants$and$animals$to$
become$adapted$to$their$environments
§
The$struggle$for$existence$ (Darwin$credits$Thomas$Malthus$for$
contributions)
○
The$most$advantageous$characteristics$are$preserved$and$passed$
onto$offspring
§
Natural$selection
○
Natural$disasters
□
Epidemics
□
Shifts$in$climate
□
Availability$of$food$and$shelter
□
Prey
□
Although$nature$can$provide$an$abundance$of$food$and$shelter$to$
its$inhabitants,$it$can$also$be$destructive,$causing$a$struggle$for$life
§
Nature$inherently$disallows$the$survival$of$some$organisms
§
Struggle$for$life
○
Each$successive$generation$of$species$exponentially$increases$its$
population,$growing$the$world$population$on$a$constant$basis
§
Therefore,$each$individual$organism$must$compete$to$
continue$existing,$and$each$individual$organism's$survival$
inherently$threatens$the$survival$of$another
□
If$each$generation$continues$to$reproduce$in$greater$numbers$than$
the$one$before,$and$the$rate$of$death$remains$the$same,$the$earth$
will$eventually$run$out$of$room$and$will$be$unable$to$support$all$of$
its$inhabitants
§
Limits$of$population$increase
○
Future$generations$are$both$dependent$on$and$essential$to$the$
perpetuation$of$advantageous$traits$and$the$progress$of$their$race
§
Most$important$is$the$struggle$between$members$of$the$same$
species
§
Survival$does$not$happen$by$chance,$it$is$the$result$of$
advantageous$variations
□
An$advantageous$variation,$combined$with$successful$reproduction,$
can$result$in$a$change$in$the$species,$creating$subspecies$better$
equipped$to$handle$its$environment
§
Survival$of$Progeny
○
One$organism$or$group$possessing$an$advantage$over$another$one$
and$beating$it$out$
§
Species$with$larger$populations$usually$have$a$greater$chance$of$
survival
§
Struggles$for$survival$are$dependent$on$others,$whether$those$
struggles$end$up$being$competitive$or$cooperative$in$nature
§
"Malthus’s$theory$provides$a$rationale$for$why$many$species$
become$extinct:$In$the$competition$to$continue$living,$the$traits$that$
allow$species$to$survive$shape$the$descent$of$new$species,$providing$
the$impetus$for$natural$selection."
§
Battle$for$limited$natural$resources
§
Mutually$beneficial$relationships:$planting$a$tree$allowing$plants$
around$it$to$flourish$-- ensures$collective$ survival
§
How$does$survival$occur$in$the$natural$world?
○
How$are$different$species$created?
•
Question$3:
Darwin$provides$examples$of$how$introduced$species$often$flourish$to$explain$his$
theory$of$natural$selection$-- claiming$that$those$with$the$most$advantageous$
characteristics$will$survive$and$pass$those$traits$onto$their$offspring.$Species$have$
naturally$adapted$over$time$to$exhibit$qualities$and$characteristics$that$will$help$them$
survive$and$thrive$in$their$environment$and$those$advantageous$variations$get$passed$
onto$the$next$generation,$almost$reshaping$that$species.$For$example,$Darwin$gives$
the$example$of$a$woodpecker,$and$how$its's$beak$is$shaped$so$that$it$can$easily$catch$
insects;$$woodpeckers'$beaks$have$evolved$so$that$they$are$the$optimum$shape$for$
efficiently$catching$its$source$of$nutrition,$$and$will$continue$to$adapt$in$order$to$
survive$changing$environments,$ecosystems,$and$competition.$
Chapter(3
Tuesday,$ September$ 20,$2016
10:02$AM
Document Summary
The struggle for existence (darwin credits thomas malthus for contributions) The determinant for which species" characteristics survive and others become extinct. Great variations in species have allowed plants and animals to become adapted to their environments. A parasite"s structure allows it to attach to and feed off another organism. Bettles" ability to dive into water an gather food. The most advantageous characteristics are preserved and passed onto offspring. Although nature can provide an abundance of food and shelter to its inhabitants, it can also be destructive, causing a struggle for life. Nature inherently disallows the survival of some organisms. Each successive generation of species exponentially increases its population, growing the world population on a constant basis. If each generation continues to reproduce in greater numbers than the one before, and the rate of death remains the same, the earth will eventually run out of room and will be unable to support all of its inhabitants.
