Transcript EVOLUTION, SEXUAL REPRODUCTION, SEXUAL DIMORPHISM,

EVOLUTION, SEXUAL
REPRODUCTION,
SEXUAL
DIMORPHISM, AND
REPRODUCTIVE
STRATEGIES
Asexual (Not Sexual) reproduction
46
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Asexual reproduction was the
only kind of reproduction from
the time of the origin of life on
earth, about 4.5 billion years
ago, up to about 1-1.2 billion
years ago, when sexual
reproduction arose.
Today:
Asexual Reproduction is limited to:
1. Prokaryotic organisms
2. Protistas
3. Fungus – Most have sexual as well.
4. Few plants – Most have sexual
reproduction as well.
5. One or two animals
Prokaryotic cells
Animal - Hydra simple Cnidaria
Protista
Plant – Grass that has runners
Sexual Reproduction
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23
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Sperm or Eggs
23
Meiosis and Mitosis Compared
Egg or Sperm (23
Chromosomes)
Human Chromosomes
Male and Females both have
46 chromosomes
44 of them are autosomes
2 are sex chromosomes
Females have XX
Males have XY
Human female karyotype
Sex Chromosomes
Human male karyotype
Sex
Chromosomes
Eggs have 23 chromosomes
22 are autosomes
1 is an X (sex) chromosome
Sperm have 23 chromosomes
22 are autosomes
The sex chromosome can be
either an X or a Y
Eggs (Ova) are large and carry a lot of
nutrients (23 chromosomes)
Sperm are small and motile – DNA with a
delivery system (23 chromosomes)
Advantages of Asexual
Reproduction
• No partner needed
• Less energy required to produce
flowers, gonads, pheromones, etc.
• Exact copy is made. So, if it works,
why change it?
Advantages of Sexual
Reproduction
• Variation
• More varieties help enable
the species to survive in a
changing environment.
Sexual Dimorphism
Physical characteristics that
differ in males and females of
the same species.
Size
Coloration
Fig. 12-06
Bill Size
Teeth and size
Horns
Explanations for the evolution
of sexual dimorphism
1. Intrasexual selection
2. Intersexual selection
3. Post-mating selection
Intrasexual
Selection
Male/Male
competition
Fig. 12-09
Usually one dominant male
Intersexual selection
Post-mating selection
In case you think all species
have sexually dimorphic sex
organs - Spotted Hyenas
In Primates sexual
dimorphism is often related to
sexual social behavior
SEXUAL SOCIAL RELATIONS:
- Monogamy – one mate for life
- Polygamy – males have multiple
partners
- Polyandry – Females have
multiple partner
Monogamy when males and females
have little or no sexual dimorphism
Polygamy
Polyandry
STUDY GUIDE FOR LECTURE I
-Sexual reproduction (Meiosis)
-Asexual reproduction (Mitosis)
-How do they differ and what are the advantages and
disadvantages of each
-Sexual dimorphism – Examples and significance
-Inter-sexual Selection – examples of characteristics and
particular animals that exhibit this.
-Intra-sexual Selection – examples of characteristics and
particular animals that exhibit this.
-Post-mating Selection – what characteristic does this
explain.
-How do sexually dimorphic characteristics in primates relate to
sexual social behavior and give examples of each.