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Flashcards in Darwin Deck (14)
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1

Acquired characteristics

John-Baptiste Lamarck (1744-1829)
▪ Differences develop in animals lifetime
▪ Passed onto offspring
▪ Eg. Giraffe & long neck

2

Darwin's Finches

▪ Darwin collects many bird species, believing them to be from several different groups
▪ All are actually finches
▪ Various types had descended from a
common ancestor
▪ Each has adapted to different foods
▪ Differences, e.g. in beak shape

3

Artificial Selection

▪ Apiece of the puzzle for Darwin.
▪ e.g. Dog breeds
▪ Common ancestor = wolf
▪ Breeds developed by breeding for desired characteristics by humans

4

Natural Selection

1. Organisms reproduce exponentially (Malthus population report)
2. Populations show variation
3. Organisms resemble parents

5

Struggle for existence

▪ Those organisms that reproduce better are ‘selected’ naturally
▪ Most species are closely matched (i.e. adapted)
to their environment
▪ Since individuals compete for resources,
▪ Environment sifts out or selects those individuals best
able to compete in that environment at that time
▪ i.e. those best adapted

6

Evolution

Over time, the genes for the most successful adaptations with increase in frequency in the population as the individuals with these genes have more chance of producing offspring as they survive longer.

7

Common Descent

Species have diverged from a common ancestor, e.g. Dogs and wolfs

8

Gradualism

Differences between species have evolved incrementally, in small steps, with intermediates - Darwin thought this was the only form of evolution, but there are also discrete steps

9

Industrial melanism in moths

Pollution from the Industrial Revolution killed lichen on trees. The melanic form was then better camouflaged on tree bark, and predation gave it a selective advantage.

10

Lack of transitional form

Darwin knew of few species in the fossil record that were
transitional in nature
▪ Since 1859, many transitional forms have been found
▪ E.g. Archaeopteryx lithographica

11

Perfection of organs e.g. eyes

Darwin was worried about explaining complex organs, such as the eye
▪ Very small advantages can produce large-scale differences over long periods of time

12

Evidence for evolution

-Fossil record
-Homology
-Vestigal organs
-Selective breeding
-Evolution in action (industrial melanism)

13

What Darwin didn't know

1. How did inheritance work?
2. Where did variation come from?

14

What Darwin was wrong about

Pangenesis - Cells give of gemmules which can effect the sex cells, allowing the transmission of acquired characteristics
Blending Inheritance- offspring get a mix of characteristics from within the bounds of the range of the parents
Retreat to Lamarckian acquired characteristics