Life Cycle Summary Diploid Life cycle Haploid Life cycle Alternation of Generations Mitosis? Meiosis? Fertilization Mitosis after meiosis? Mitosis after.

Life Cycle SummaryDiploid Life cycle

Haploid Life cycle

Alternation of Generations

Mitosis?

Meiosis?

Fertilization

Mitosis after meiosis?

Mitosis after fertilization?

Multicellular diploid stage?

Multicellular Haploid Stage?

Yes Yes Yes

Yes Yes Yes

Yes Yes Yes

No Yes Yes

Yes No Yes

Yes No Yes

No Yes Yes

Evolution: Classically: A change in the relative

frequencies of heritable traits within a population across generations

Relative frequency:

50% Tall plants 50% Short plants

55 generations later

25% Tall plants 75% Short plants

Modern: A change in the distribution of relative frequencies of genes (which code for heritable traits) within a population across generations

Requirements for Evolution to occur:

Variation in traits [via genes (alleles)]

Heredity

Darwin’s Observations Biogeography: species are distributed in

distinct clumps across the globe

Biogeography: species are distributed in distinct clumps across the globe

Fossils Evidence of organisms no longer present

Evidence that many living organisms were not present in the past.

Today10,000 years ago

2 million years ago

5.5 million years ago

24 million years ago

34 million years ago

Moeri-therium

Bary-therium

DeinotheriumMammut (mastodon)

Platybelodon

Stegodon

Elephas maximus(Asian elephant)

Mammuthus(mammoth)

Loxodonta africana(African savannah

elephant)

Agriculture: Selective breeding

Agriculture: Selective breeding

About 250 million years agoPlate tectonics

Plate movements and geological studies indicated the earth was older than the estimated 6,000 years

Figure 14.20

Mill

ion

s o

f ye

ars

ago

Ce

no

zoic

Me

so

zoic

Pa

leo

zoic

North Americ

a

Eurasia

SouthAmerica

Africa

IndiaMadagascar

Antarctic Australia

Laurasia

Gondwana

Pangaea

Economics: Competition for resources and the effects of overpopulation

Struggle for existence

Evolution by Natural Selection (a mechanism of evolution) Population level:

If variation exists and If variation is heritable and If differential reproduction (differential selection) exists

Then over time, those variations that enhance the ablitiy of the organism to reproduce will increase in any population

Mutation occurs in the trait Mutation directly changes gene frequencies

An example of a spontaneous mutation during the development of plant leaves

For evolution to occur via this mechanism, what has to be true of the mutation?

The mutation has to be heritable

The mutation of fruit flies with four wings is an inherited mutation

The population size is small

Genetic drift – random fluctuations in the allele frequencies

Generation 1p (frequency of R) = 0.7q (frequency of r) = 0.3

Only 5 of 10 plantsleaveoffspring

Generation 2p = 0.5q = 0.5

Only 2 of10 plantsleave offspring

Generation 3p = 1.0q = 0.0

Gene flow

Immigration or emigration occurs based on the trait

Sexual Selection

Mating is non-random in the population with respect to the trait

Which mechanism leads to adaptation to the environment?

Natural selection: Adaptations are traits that increase the probability that an organism will survive and reproduce in the current environmental conditions.

What is an adaptation?

A heritable characteristic of an organism that helps it to survive and reproduce in a particular environment.

Mimicry of a poisonous animal will increase the probability of survival and survival until the organism is able to reproduce

Example: Marine Iguana

Adaptations do not have to be one trait, they can be a suit of traits

“The guanas are small, and of a sooty black, which, if possible, heightens their native ugliness. Indeed, so disgusting is their appearance, that no one on board could be prevailed on, to take them as food.” Captain James Colnett (1798)

Flattened tail – aids in swimming Salt gland – Allows drinking of salt water Long, sharp claws – Aid in clinging to rocks Diving adaptations. While diving they:

Reduce blood flow to body surface- helps retain heat

Lower metabolic rate – conserves O2

Adaptation refers to traits that are heritable Acclimation: Changes in the structure or physiology of an

individual over its lifetime

Examples: Increasing muscle mass via weightlifting

High altitude acclimation:

Organizational level evolution occurs? Living organisms display a natural

hierarchy of organization and emergent properties that are more than the simple sum of their parts

Atoms lead to Molecules, which lead to Organelles, which are arranged

within Cells, which make up Tissues, which make Organs, which form Organ systems, which together

make an Organism, which is part of a Population within a Community in an Ecosystem, the largest of which is

the Biosphere (=Earth)