L.Kleyn Page 1 of 3
1
Reproductive strategies Advantages Disadvantages
External fertilisation - new individual by fusion of gametes from 2 parents 1. aquatic environment maximises 1. environment has to be safe,
Egg and sperm released simultaneously -swim in water to fert. egg - reproductive success - water facilitates environment unprotected, must not
Reproductive Synchrony ; aquatic organisms, many eggs and sperm are fertilisation desiccate *conditions = important
🌊
released = no energy ,parental care or formation of shell(protective) 2. not particularly successful -
destroyed, drift apart, eaten,
Sessile: coral, anemones, mussels, barnacles, oysters
damaged, fail to reach egg
🐚🐸🐡🐟
Internal fertilisation - new individual by fusion of gametes from 2 parents 1. gametes not exposed to conditions that 1. requires reproductive behaviours -
copulation - penis + vagina, male inseminates the female-egg fert. inside female would cause them to dry out courtship; offspring born in a season/
Egg in all vertebrates except mammals, placenta for mammals 2. embryos not lost to predation or time when environment is suitable for
🐢🐝🐦🚶
washed away (contained environment) survival
3. parental care1 2. source of food required-food for
*
developing embryo is supplied by egg
1 Parental care:
1. Precocial 2. Altricial
• mature young - helpless young
• longer gestation period - naked
• active and mobile immediately after birth - born small-brained but with rich diets, develop bigger brains
• bigger brain at birth - cant walk or fly
• hair / fur - shorter gestation period
• open eyes - totally reliant on parents (very vulnerable at birth)
• less reliant on parents - closed eyes
1
Reproductive strategies Advantages Disadvantages
External fertilisation - new individual by fusion of gametes from 2 parents 1. aquatic environment maximises 1. environment has to be safe,
Egg and sperm released simultaneously -swim in water to fert. egg - reproductive success - water facilitates environment unprotected, must not
Reproductive Synchrony ; aquatic organisms, many eggs and sperm are fertilisation desiccate *conditions = important
🌊
released = no energy ,parental care or formation of shell(protective) 2. not particularly successful -
destroyed, drift apart, eaten,
Sessile: coral, anemones, mussels, barnacles, oysters
damaged, fail to reach egg
🐚🐸🐡🐟
Internal fertilisation - new individual by fusion of gametes from 2 parents 1. gametes not exposed to conditions that 1. requires reproductive behaviours -
copulation - penis + vagina, male inseminates the female-egg fert. inside female would cause them to dry out courtship; offspring born in a season/
Egg in all vertebrates except mammals, placenta for mammals 2. embryos not lost to predation or time when environment is suitable for
🐢🐝🐦🚶
washed away (contained environment) survival
3. parental care1 2. source of food required-food for
*
developing embryo is supplied by egg
1 Parental care:
1. Precocial 2. Altricial
• mature young - helpless young
• longer gestation period - naked
• active and mobile immediately after birth - born small-brained but with rich diets, develop bigger brains
• bigger brain at birth - cant walk or fly
• hair / fur - shorter gestation period
• open eyes - totally reliant on parents (very vulnerable at birth)
• less reliant on parents - closed eyes
