2-2 sexual reproduction in animals - despite the variety amongst the many animals, they still...

2-2 Sexual Reproduction in Animals- Despite the variety amongst the many animals, they still reproduce

sexually the same- meiosis produces gametes- male gamete (sperm) combines with female gamete (egg)- a zygote is produced and develops into an embryo- embryo develops by mitosis into mature offspring

For success 2 things must happen- Both male and female gametes arrive in same place at same time- Zygote must receive adequate food, moisture, warmth, and protection to develop

Mating Patterns in Animal Kingdom- 2 members of a population come together to combine gametes for

fertilization- in some only one mating season/year (usually when offspring will

hatch or be born in favourable conditions)- fish called grunion mates when tide is high, honeybee mates once in

lifetime

Mating Patterns in Animal Kingdom- 2 members of a population come together to combine gametes for

fertilization- in some only one mating season/year (usually when offspring will

hatch or be born in favourable conditions)- fish called grunion mates when tide is high, honeybee mates once in

lifetimeFertilization Patterns

- occurs only if sperm meets an egg from same species- moist environment is required so gametes don’t die- egg’s cell membrane supple - sperm need water to swim

2 Patterns of Fertilization External - sperm and egg meet outside bodies - (mostly

aquatic) Internal - sperm travels from male’s body into female’s body to meet the egg – development internal or external

2 Patterns of Fertilization External - sperm and egg meet outside bodies - (mostly

aquatic) Internal - sperm travels from male’s body into female’s body to meet the egg – development internal or external

External Fertilization - mostly water-dwelling animals Sea anemone - Adult anemones – cannot move around to mate with each other - Release eggs and sperm directly in water - rely on currents to

carry gametes together - Zygotes = free-swimming, self-feeding larvae which travel distances before settling down and developing into adultsFish - female lays cluster of eggs, male releases sperm directly over

eggs (spawning)Frogs - Mating – male frog embraces female who lays her eggs while

male releases sperm over them- young hatch from eggs of anemones, fish, frogs and do not

look like adult forms- Undergo many developmental changes to become adult

forms – some live in water, others move to land

Frogs - Mating – male frog embraces female who lays her eggs while male releases sperm over them

- young hatch from eggs of anemones, fish, frogs and do not look like adult forms

- Undergo many developmental changes to become adult forms – some live in water, others move to land

Internal FertilizationMostly land animals – need specialized structures on male to transfer

sperm directly to femaleReptiles - males transfer sperm into female’s cloaca (chamber where

female reproductive, urinary and digestive ducts leave body)- most reptiles lay eggs with tough, leathery shells with a

fluid- filled sac surrounding the zygote – embryoBirds - few have specialized structures for transferring sperm, both

males and females have cloaca - fertilization by close contact where the sperm swim from male cloaca to female cloaca - eggs laid with hard outer coverings – birds incubate, protect

Birds - few have specialized structures for transferring sperm, both males and females have cloaca - fertilization by close contact where the sperm swim from male cloaca to female cloaca - eggs laid with hard outer coverings – birds incubate, protect

- most species – parents invest a great deal of energy in feeding young- some animals are born as miniature adults while others pass through

different stages of development Incomplete metamorphosis (grasshoppers, crickets, frogs pass) larval form has similarities to adultComplete metamorphosis (houseflies, butterflies) -adult form does

not look like earlier stages- some mothers retain and nourish young before birth which ensures

additional development, protection- Mammals produce milk for nourishment of their young

Complete metamorphosis (houseflies, butterflies) -adult form does not look like earlier stages

- some mothers retain and nourish young before birth which ensures additional development, protection

- Mammals produce milk for nourishment of their youngHermaphrodites

- Animals that have both female and male reproductive organsFlatworms – planarians – during mating, each planarian injects sperm

into a reproductive pore on other flatworm’s body - each lays fertilized eggs

Earthworm – also hermaphroditeInternal fertilization – ensures sperm has moist environments to travel and increases chances that the eggs will be fertilized