External vs Internal

External Reproduction

Fertilisation happens outside.
Lots of aquatic animals use (fish, jellyfish, amphibian)
Sperm can swim in water, wont dry out

Internal Reproduction

Fertilisation happens inside
All land animals and some aquatic animals=internal fertilisation because sperm dry out

Copulation

The act of sex, where male sperm is transferred to the female
there are different ways this can happen

Development

changes in form and structure in an individual over its life, from zygote → adult

Growth

increase of cell number through mitosis

External development

young develop in a structure such as an egg e.g. spiders, insects

External development disadvantage

little to no parental care → high number of offspring die (Most fit survive → better adapt to that env)

External development advantage

high number of offspring produce → high efficiency. Little energy = invested by mum

Internal development

young develop inside the female’s body, usually in the uterus (womb) e.g. placental mammals (cat, dog, whale)

Internal development disadvantage

fewer offspring produce → low efficiency (only small number can fit in womb)

2 parents required

Internal development advantage

High level of parental care → more offspring can survive

Part external, part internal (Marsupil mammals)

underdevelopment young born live, development continue in mum pouch

monotreme mammals

young develop outside parent pouch, inside a structure such as egg e.g platypus

R strategy

short lived, weak, preyed upon.
live in unpredictable env→ flood env with many offspring because of nat. selection, some may survive to adult

R strategy charecteristics

many offspring
dont care for offspring
offspring = mature quickly

K strategy

larger, stronger, better protected + longer live. Stable env → fewer offspring which they spend more time + energy to care for → offspring more likely to survive

K strategy characteristics

few offspring
care for offspring
offspring mature slowly

R strategy vs K strategy

R strategy
- reproduce asexually
- externally develop offspring

K strategy
- reproduce sexually
-internal development offspring