Natural Selection, Evolution & Implications for the Conservation of Wildlife
Evolution It’s the process that drives- • the diversity of reproductive strategies we’ve studied… • the ongoing relationships between predator and prey… • the patterns of wildlife distributions around the globe… • responses to disturbances… • guides the migrants… • as well as the demise of all the species that have become extinct throughout all of time…
Taxonomy: Birds Class Aves (birds) Order Anseriformes (ducks, geese, swans, and relatives) Order Galliformes (chicken-like birds) Order Caprimulgiformes (nightbirds) Order Apodiformes (hummingbirds and swifts) Order Balaenicipitiformes (shoebill or whale-headed stork) Order Charadriiformes (shorebirds and relatives) Order Ciconiiformes (storks and relatives) Order Coliiformes (mousebirds) Order Columbiformes (doves and pigeons) Order Coraciiformes (kingfishers and relatives) Order Cuculiformes (cuckoos and relatives) Order Falconiformes (diurnal birds of prey) Order Galbuliformes Order Gaviiformes (loons) Order Gruiformes (coots, cranes, and rails) Order Mesitornithiformes (mesites) Order Musophagiformes (turacos) Order Opisthocomiformes (hoatzin) Order Passeriformes (perching birds) Order Pelecaniformes (pelicans, tropicbirds, cormorants, and relatives) Order Phoenicopteriformes (flamingos) Order Piciformes (woodpeckers and relatives) Order Podicipediformes (grebes) Order Procellariiformes (tube-nosed seabirds) Order Psittaciformes (parrots) Order Sphenisciformes (penguins) Order Strigiformes (owls) Order Trogoniformes (trogons) Order Turniciformes (buttonquail) Order Struthioniformes (cassowaries, emus, kiwis, ostriches, and rheas) Order Tinamiformes (tinamous)
And even for humans, it drives …and who will not who will survive…
Nothing in biology makes sense except in the light of evolution” -Theodosius Dobzhansky Evolution through natural selection is the foundation of modern ecology, biology and medicine.
Theory or Fact? • In everyday vernacular, a theory is “a guess”. • As a scientific term, a theory is “a statement of what are held to be the general laws, principles, or causes of something known or observed” (OED) • A scientific theory is testable and can make verifiable predictions • In fact, it has been noted that we know more about the mechanisms of evolution than we do gravity, the nature of light, sleep, the weather, and something even more nebulous and stormy… love.
Throughout much of human history, the dominant perspective (and still is in some of the less educated parts of the world… and country), was that everything was divinely created in its present form, and that this Creator also orchestrated their interactions not unlike a master puppeteer.
Theologist: “ What have you learned about the mind of God in the course of your studies of biology?” J.B.S.Haldane: “ Madame, only that he had an inordinate fondness for beetles.”
Charles Darwin(1809-1882) Published one of the most influential books ever written- On the Origin of Species- in 1859 2009 marks the 200th anniversary of his birth and 150th anniversary of the publication of OtOoS
What is Natural Selection? “principle by which each slight variation [of a trait], if useful, is preserved” – Darwin
Natural Selection • Individuals within populations are variable for nearly all traits • Individuals pass on their genes to offspring • More offspring are produced than can survive • Individuals that survive and go on to reproduce (the most) are those with the varieties (alleles) that best adapt them to their environment • Outcome: alleles associated with higher fitness increase in frequency from one generation to the next
Natural Selection is also a part of population regulation • The reproductive potential of populations is great, but • populations tend to remain constant in size, because • populations suffer high mortality. • Individuals vary within populations, leading to • differential survival of individuals. • Traits of individuals are inherited by their offspring. • The composition of the population changes by the elimination of unfit individuals • Rabbits should cover the earth, but • they don’t, because • many are caught by predators. • Some rabbits run faster than others, • and escape from predators • and so do their young. • Populations of rabbits, as a whole, tend to run faster than their predecessors. From Ricklef’s “The Economy of Nature” Second Edition
Important Points • Weak forces operating over long periods of time create large and dramatic change. • Natural selection is the non-random survival of random variants • Natural selection- by itself- is not evolution. It is the mechanism that can lead to evolution. • Natural selection takes place within a generation, but evolution takes place across generations.
Watson & Crick Mechanism of inheritance DNA 1953 Gregor Mendel Contemporary of Darwin “father of genetics” -1866 Heritable traits & dominance
Graph showing the distribution of beak depths for medium ground finches in Year 1 34
la Niña = Drought el Niño = Rains
Drought (la nina) Wet (el nino)
Following the drought of 1977, 85% of the medium ground finch population died. In 1975, the rainy season came and went with nary a drop of rain (el Niño)
Year 3 Data 40
This demonstrates natural selection, but the story is not quite over… • The year of the drought, no young were produced • After the drought, the 15% that survived represented birds with larger bills. • These individuals did breed the following year. • What do think their offspring looked like? (Small beaks? Medium beaks? Big beaks?) • This is evolution.
Other evidence for evolution • Common structures (homologous) • Analogous structures (convergent evolution) • DNA Research • Fossil Record • Embryonic development • Vestigial Organs & Structures • Imperfections in Structure • Drug-Resistant Bacteria
Convergent Evolution~ Physical adaptations to similar ecological conditions~
DNA - species that appear to be more distantly related from their positions in the fossil record are found to have correspondingly greater differences in their DNA than species that appear more closely related in the fossil record.