Reproduction & Development I. Selective Forces -- all of evolution is based on reproduction -- to persist through evolutionary time, animals must put copies of their genes into the next generation -- for sexual reproduction, fertilized egg must develop into surviving offspring

Reproduction II. Asexual vs. Sexual Reproduction A. Asexual reproduction -- only one parent -- no reproductive organs -- no meiotically produced gametes (sex cells); no fertilization or zygote formation -- offspring are genetically identical to parents (clones)

Reproduction II. Asexual vs. Sexual Reproduction A. Asexual reproduction 1. advantages -- pass on 100% of genome to each offspring -- all individuals can produce offspring directly -- can occur rapidly; rapid exploitation of resources -- saves energy and resources (no gonads or gametes, no finding mates, no courtship, no STDs, no males) 2. disadvantages -- no genetic variability in offspring (except for random mutations) -- limited ability to respond to changing environment

Reproduction II. Asexual vs. Sexual Reproduction B. Sexual reproduction -- usually involves two parents -- reproductive organs -- haploid gametes produced by meiosis; fertilization  diploid zygote -- offspring are genetically unique 1. disadvantages -- pass only 50% of genome to each offspring -- energy expended for gonads and gametes -- production of males (many fail to mate) -- is complicated; occurs more slowly -- requires finding mates, courtship, -- STDs 2. advantages -- increased genetic variability in offspring -- ability to respond to changing environment, esp. biotic environment

Alternation of Asexual and Sexual Reproduction: ex: Fasciola (sheep liver fluke) Sexual adult in sheep liver egg metacercaria; encysted on vegetation asexual redia in snail miracidium Asexually produced cercaria; leave snail

Reproduction III. Mechanisms of Asexual Reproduction A. Fission: animal divides by mitosis Binary fission Paramecium Multiple fission Plasmodium

Binary Fission Asexual Cell splits and replicated DNA goes with each part Prokaryotes, Bacteria + Fast and easy - Everybody has the same DNA

Bacterial Conjugation Asexual “Sex” A bacteria shoots out a tube and sends a piece of its DNA to another bacteria Bacteria + Mixes DNA - “Parent” loses a little piece of DNA

Fragmentation/ regeneration  Asexual  Body of parent breaks and produces offspring  Fungi, moss, sea stars, planarian  + Easy  - Parent broken, same DNA

Fragmentation/ regeneration

Reproduction III. Mechanisms of Asexual Reproduction B. Budding: new individual arises from outgrowth of parent

Reproduction III. Mechanisms of Asexual Reproduction C. Gemmulation: Poriferans -- formation of new individual from aggregation of asexual cells encased in resistant capsule (= gemmule)

Reproduction III. Mechanisms of Asexual Reproduction D. Fragmentation: -- formation of new individual from fragments of parent